The phrase part of speech refers to an identifying label given to a word based on how it is used in a sentence.  Although lists of these labels may differ slightly, grammar books traditionally list eight parts of speech:  noun, pronoun, verb, adjective, adverb, conjunction, preposition, interjection.*

Before learning the parts of speech, it is useful to understand why we bother with these classifications in the first place.  In brief, having labels for how words function in a sentence helps us to understand better how sentences are constructed and therefore makes us more skillful at putting sentences together.

We can construct sentences without knowing what the parts of speech are, just as we can probably drive a car without knowing the names for the accelerator and the brake.  However, we're in big trouble if we don't know that the accelerator causes the car to go faster whereas the brake causes it to slow down or stop.  We're also in big trouble if, when we're learning to drive, our instructor tells us to hit the brake and we step on the accelerator instead because we don't know the difference.  We have a similar handicap when learning how to write if we don't know the difference between, say, a noun and a verb or what these parts of speech do.

Yes, one can write without even having heard of nouns, pronouns, verbs, adjectives, adverbs, conjunctions, prepositions, and interjections – but knowledge of these terms and their meaning is an important tool for helping us understand how writing works, how to "drive" our sentences, so to speak.  Conversely, memorizing these terms and their definitions is no guarantee that we will write effectively; it is only a means to an end, not the end itself.

*One common variation is to list articles (the, a, an) as a distinct group, but most sources include articles among the adjectives.

This article has three main divisions (you may jump directly to each by clicking on its title) –
> Basic Definitions
> Some Details (tips that will help you to recognize and use the parts of speech)
> Subdivision of and Rules Pertaining to Parts of Speech (breakouts of types of words within the eight basic classifications, where applicable, including, at the end, a discussion of verbals – verb forms used as other parts of speech)

Basic Definitions

The names of the parts of speech have been linked to further discussions.  Click on the name of the part of speech to go to the further discussion in the unit titled "Now, Some Details."  Similarly, in the details unit, click on the name of the part of speech to go to even more comprehensive and advanced material in the "Subdivision of and Rules Pertaining to Parts of Speech" section.  (We have not bothered to link interjections because few further details are given about this part of speech.)

Nouns label something by name – a person, a thing, a place, a quality, or an idea.

Pronouns are used as substitutes for nouns (in place of nouns) and function as a noun does.

Verbs express action, an occurrence, or a state of being.

Adjectives describe, limit, qualify, or in some other way modify a noun or pronoun.

Adverbs describe or modify verbs, adjectives, or other adverbs; they may also modify complete phrases, clauses, or sentences.

Prepositions precede nouns or pronouns (plus any of their modifiers) to form a word group called a prepositional phrase.  These phrases usually function in the sentence as modifiers.

Conjunctions connect words, phrases, clauses, or sentences.

Interjections are exclamations, used to express feeling or command attention.

Now, Some Details

Click the name of the part of speech in the discussions below to go to even more in-depth discussion of that part of speech.

► Remember that a certain word by itself (when it is not being used in a sentence) does not "have" a part of speech.  Although some words (for example, most prepositions and conjunctions) can be used as only one part of speech, many words can function as different parts of speech depending on how they are used in a sentence.  Help, for instance, could be a verb ("Please help me"), a noun ("I need your help"), or an adjective ("Go to the help desk" – help modifies the noun desk).

► Nouns not only name persons ("Bob Jones is our neighbor"), living things ("Our cat has fleas"), physical objects ("The keys are in the door"), or places ("New York is a big city"); they are also labels for qualities ("Intelligence is important"), concepts ("We demand justice"), emotions ("Love conquers all"), abstractions ("She is seeking wisdom"), and so on.  [The nouns are in italics.]  Nouns serve as subjects or objects or may be used to indicate possession.

► Pronouns.  The words that immediately come to mind as pronouns are the personal pronouns:  I, you, he, she, it, we, and they in their various forms.  However, other words may function as pronouns (noun substitutes).  For example, words such as each, many, anyone, and one may be used as pronouns (specifically as indefinite pronouns).  Words such as who or which may be used as either relative pronouns or interrogative pronouns.  For discussion of types of pronouns, see Subdivisions of Parts of Speech (below).

Nouns and pronouns have a quality called case; they may be nominative, objective, or possessive.  When used as subjects, they are in the nominative case.  When used as objects, they are in the objective case.  When used to indicate possession, they are in the possessive (sometimes called "genitive") case.  English nouns have the same form in both the nominative and objective cases.  They change form only in the possessive case (see the article titled Possessive Nouns: The Apostrophe on this site).  Some of the personal pronouns, however, have different forms in the nominative and objective cases.  For example, nominative he becomes objective him (possessive = his).

► Verbs.  Since most verbs are action words, they will fit in the blank in a sentence such as, "You can ______ something."  Therefore, we know that read, do, believe, and like can be verbs.  We can read something, do something, believe something, or like something.  We know that among, because, tall, and tomorrow cannot be verbs – we cannot among something, because something, tall something, or tomorrow something.

Although some verbs won't work in "You can _____ something" because they cannot take an object*, that's still a fairly good test of whether a word can be used as a verb.  Belong is an example.  We cannot belong something (though we can belong to someone or something), but it is a verb (in fact, it can be used only as a verb).
*Verbs that cannot take objects are called intransitive verbs.

It's also worth noting that verbs don't always designate what we think of as actions.  We don't think of happen as an action; happen is one of those few verbs that designate an occurrence (as in, "It happens every day").  We don't think of be (in its various forms such as is and are), seem, or remain as actions.  They are among the verbs that designate a state of being (as in, "He is handsome," "It seems hot," and "The job remains incomplete").

Every sentence must have a verb, which is often the most vital element in the meaning of the sentence.  Therefore, please take special note of the discussion of verbs above and of the points raised under Subdivisions of and Rules Pertaining to Parts of Speech (below).

(At the end of this article is a discussion of verbals – verb forms that function not as verbs but as other parts of speech.  Click here to go directly to that discussion.)

► Adjectives and Adverbs.  The function of adjectives and adverbs is to modify other words in the sentence.  That is, they add more information about the word, limit it, or qualify it in some way.

Because they modify only nouns and pronouns, adjectives are fairly easy to identify.  Thus, when we say that "Mary is a pretty woman," the adjective pretty modifies the noun woman.  Likewise, when we say that "Mary is pretty," pretty modifies the noun Mary.  No, it does not precede the noun Mary, but it still gives us more information about Mary and thus modifies Mary.  It is what we call a predicate adjective because it appears in the predicate of the sentence – the part of the sentence that includes the verb and all the words that follow it.  (Predicate adjectives always follow linking verbs, such as appear, seem, become, feel, look, and the various forms of be.)

Because adverbs modify verbs, adjectives, other adverbs, or entire word groups, including complete sentences, they are a little more complicated.  Adverbs answer the questions "How?" "Why?" "Where?" "When?" "Under what conditions?" or "To what extent?"  Examples:  In "He walked slowly," slowly is an adverb modifying the verb walked.  It tells how he walked.  In "He is going tomorrow," tomorrow is an adverb telling when he is going; it could therefore be said to modify all of the rest of the sentence, "He is going."

► Prepositions.  These words may be regarded as relationship words.  They are used to show the relationship of nouns or pronouns (along with their accompanying modifiers) to the rest of the sentence.  Most of the commonly used prepositions are short words (by, in, for, from, at, with, etc.), but some are longer (between, among, concerning, throughout, etc.), and some may consist of more than one word (instead of, except for, in addition to, etc.)

Like conjunctions (see below), prepositions have meaning but do not have substantive meaning.  That is to say, they do not, by themselves, label anything, describe a quality or condition, or depict an action.  They serve only to show relationships of words or word groups to one another.

► Conjunctions are link words.  They may coordinate two or more words or ideas, as and or but do ("Mary and Jane are sisters, but they do not always agree"), or they may subordinate one idea to another ("They often argued when they spent a lot of time together").  A third group of conjunctions, called correlatives, operate in pairs (either . . . or, neither . . . nor, not only . . . but also, and others).

► Interjections.  These are usually single-word exclamations (Oh!  Wow!) and are rarely used in academic or business writing.
 

Subdivisions of and Rules Pertaining to Parts of Speech

Types of Nouns

Common Versus Proper Nouns.  Common nouns label general classes of things and do not begin with a capital letter:  man, person, family, house, city, document.
Proper nouns label specific places and things and begin with a capital letter:  Albert Einstein, Mr. Jones, the Smiths, the White House, New York, the U.S. Constitution.

Count Versus Noncount Nouns.  Count nouns name things that can be counted (e.g., penny).  Most add -s or -es to distinguish between singular (one) and plural (two or more) — one penny, ten pennies.  Some count nouns have irregular plurals (one person, two people; one woman, several women; one child, a number of children). 
Noncount nouns label things that are not countable (e.g., the word money – yes, we can count money, but we don't say "one money, two moneys").  They also name qualities (e.g., courage, happiness, wisdom).  Noncount nouns do not form plurals.
Caution:  Some nouns may be either count nouns or noncount nouns, depending on how they are used.  For example, truth in the abstract is a noncount noun ("He told the truth"), but it could be a count noun when it refers to a specific true idea ("We hold these truths to be self-evident").

Collective Nouns.  These nouns label groups and are singular in form.  They are treated as singular when they refer to the group as a unit ("The family is going on vacation") but as plural when they refer to the individuals in the group separately ("My family [meaning members of my family] live [plural verb] in many different states").

Types of Pronouns

Personal Pronouns refer to a specific individual or to individuals (or, in the case of it, to a specific thing).  In the nominative case, these pronouns are I, you, he, she, it, we, and they.  In the objective case, they are me, you, him, her, it, us, and them.  The possessive forms are:  my (or mine); your (or yours); his; her (or hers); its; our (or ours); and their (or theirs).

We label the personal pronouns by using the terms "first person," "second person," and "third person."  The first-person nominative singular pronoun is I, and the first-person nominative plural pronoun is we.  The second-person nominative pronoun (both singular and plural) is you.  The third-person nominative singular pronouns are he, she, and it; their plural is they.

Indefinite Pronouns – such as everybody, some, all, and none – do not substitute for any specific nouns, though they function as nouns.

Relative Pronouns (who, whoever, which, that) relate words or groups of words to nouns or other pronouns:  "The hat that she wore was hideous."  "People who live in glass houses should close their curtains."

Interrogative Pronouns – such as which, who, and what – introduce questions:  "What do you think?"

Demonstrative Pronouns – such as this, that, and such – identify or point to nouns:  "This is a penguin, but that is a walrus."

Intensive Pronouns add -self or -selves to the personal pronoun:  myself, yourself (plural yourselves), himself, herself, itself, ourselves, themselves.  These pronouns emphasize a noun or other pronoun:  "He himself is unsure of the solution."

Reflexive Pronouns have the same form as intensive pronouns.  They indicate that the sentence subject also receives the action of the verb:  "The man [subject] injured himself."  "We enjoyed ourselves."

Worth Noting:  Some words that function as pronouns may have other functions.  For example, in the previous sentence, some functions not as a pronoun but as an adjective modifying words.

Forms, Qualities, and Types of Verbs

► Every verb has four principal parts – a base form or plain form (the form of the verb that appears in the dictionary and that is used with I, you, we, and they in the present tense)*; a present participle (the -ing form of the verb); a past tense form; and a past participle (the form used in the perfect tenses along with have, has, and had).
*The verb be is so irregular that it is an exception to this definition; its base or plain form is be, but it is not correct to say, "I be," "He be," "We be," etc.

► When another verb is used along with the main verb, this verb is called an auxiliary verb (or, more simply, a helping verb).  These verbs indicate tense, mood, or voice – or, to put it another way, they indicate time, possibility, obligation, and other kinds of meaning.  In "He is sleeping," for example, the auxiliary verb is is combined with the main verb sleeping to indicate time (present tense).  In "The work was done by noon," the auxiliary verb was is combined with the main verb done to indicate past tense.  This combination of a form of be (was) and the past participle of the main verb (do – past participle = done) creates a passive voice construction (see the discussion of voice below).

Among the auxiliary verbs are those known as modal auxiliaries – helping verbs used to indicate necessity, possibility, willingness, obligation, or ability.  Verbs used as modal auxiliaries include must, would, should, may, might, can, and could.  The auxiliaries will and shall function both as modal auxiliaries and as indicators of future tense.  Examples:  In "You must go," the modal auxiliary must indicates necessity or obligation.  In "I might do it," the modal auxiliary might indicates possibility. 

► The verb quality that we call tense refers to a change in the form of the verb that indicates the time when the action denoted by the verb took place.  English verbs have six basic tenses – present, past, future, present perfect, past perfect, and future perfect.  In addition, each of these has a progressive (also called continuous) form, used primarily to denote ongoing action.  Use of the various tenses is described here on this website.

► Verbs also have number (they may be singular or plural).  When its subject is singular, the verb must be singular; when its subject is plural, the verb must be plural.  In English, we are not concerned with a verb's number in past, future, past perfect, and future perfect tenses because, in these tenses, the verb has the same form in singular and plural.  However, in the present and present perfect tenses, the third-person singular verb takes a different form.  For example, in the present tense, the verb go becomes goes in the third person singular – "I, you, we, or they go," but "he, she, or it goes."  In the present perfect tense, the helping verb have or has is used, with has as the proper verb for the third person singular – "I, you, we, or they have gone," but "he, she, or it has gone."  (For more about subject-verb agreement, see this article on this website.)

► Another quality that we occasionally mention when talking about verbs is mood.  There are three moods – indicative, imperative, and subjunctive.  The indicative mood is used when we state a fact, express an opinion, or ask a question.  It is therefore what we use most of the time.  The imperative (which consists of the base form of the verb without a subject) is used to give a command ("Get lost") or to express a request ("Please pay the cashier").

The subjunctive mood causes the most difficulty for students.  The present subjunctive uses the base form of the verb, regardless of what the subject is.  It is used in clauses beginning with that after words such as ask, request, demand, require, insist, recommend, and suggest.  (Examples: "I suggest that you be honest." "I recommended that she take the bus.")  The past subjunctive has the same form as the past tense of the verb.  It is used in conditional statements – those beginning with if that are contrary to fact, including statements that expresses a wish.  (Examples:  "He acted as if he knew the answer."  "If I were you, I wouldn't do that."  "I wish I were more organized.")*
*In the subjunctive, the verb be takes the form were regardless of the person or number of the subject. 

► Verbs also have voice – a quality that can have a profound impact on style.  There are two voices – active and passive.  Voice indicates whether the subject acts (active) or is acted upon (passive).  In "He decided," for example, the subject (He) acts upon the verb (decided) – active voice.  In "It was decided by him," the subject (It) is acted upon (is the recipient of the action) – "was decided" is passive voice.

The passive voice is formed by using a form of be (be, am, is, are, was, were, being, been) followed by the past participle of the verb, as in, "The work was completed in two days" and "Her book will be published by Random House."  [The active voice versions, respectively, are "They completed the work in two days" and "Random House will publish her book."]

Active voice is usually briefer, clearer, and more emphatic than passive voice.  Therefore, although situations exist in which passive voice is appropriate (e.g., when the actor is unknown or is less important than the object of the action) and sometimes even unavoidable, try to use active voice whenever possible.

Adjectives and Adverbs:  Form and Function

Both these types of words add substance to sentences by describing, limiting, qualifying, or in some other way modifying another word or group of words.  As noted in the basic definitions, we differentiate adjectives from adverbs by what they modify.

► All adjectives and adverbs have comparative and superlative forms.  Comparatives indicate comparisons between two qualities (greater or lesser).  Superlatives indicate comparisons among three or more qualities (greatest or least).
   ♦  Comparatives.  All one-syllable adjectives and many two-syllable adjectives (mostly those ending in -y, -ly, -le, -er, or -ow) add -er to form the comparative:  slower, happier.  Other two-syllable adjectives and all long adjectives use more:  more handsome, more difficult.  Adverbs ending in -ly (as a majority of adverbs do) use more for the comparative:  more slowly, more carefully.  Other adverbs add -er (or -r):  sooner, later.  To indicate a lesser degree, all adjectives and adverbs use less in the comparative:  less beautiful, less quickly.
   ♦  Superlatives.  Adjectives that form the comparative by using -er add -est to form the superlative:  slowest, happiest.  Adjectives that use more in the comparative use most for the superlative:  most handsome, most difficult.  The majority of adverbs use most to form the superlative:  most slowly, most carefully.  A few add -est:  soonest, latest.  To indicate the least degree, all adjectives and adverbs use least in the superlative:  least beautiful, least quickly.

► Beginning writers sometimes overuse the modifiers.  Instead of clarifying the mental image, excessive modifiers may make it fuzzy.  They contribute to wordiness.  "It was a bright, clear, cloudless, sunny summer day" is adjective overkill.  Furthermore, one can sometimes include in the verb itself the meaning conveyed by the adverb, thus eliminating the need for an adverb.  For example, instead of writing "He ran quickly" (verb + adverb), we can write "He raced" or "He dashed."

About Prepositions

► The meanings of most prepositions are idiomatic – that is to say, what they mean is highly dependent on the context in which they are used.  For example, the preposition in used in the context of "in the morning" refers to time; in "in the house," it refers to place; in "in my opinion," it refers to something else and means something like "according to."  Moreover, we can sometimes use two prepositions interchangeably in the same context with little, if any, difference in meaning:  "on time" and "in time" are both possible and have roughly the same meaning; however "on my head" and "in my head" have entirely different meanings.  In addition, the same two prepositions may be interchangeable (with or without differences in meaning) in one context, but one of them may be completely inappropriate in another context:  "in my opinion" makes sense, but "on my opinion" does not.

Native speakers of English usually have few problems with using the appropriate preposition, but this "idiomatic" quality of prepositions poses huge difficulties for non-native speakers.  Still, native speakers may sometimes err.  For instance, "to drive in to [two words] a bank" and "to drive into [one word] a bank" have different meanings.  The first means merely that we drove to the bank, but the second means that we collided with it (possibly by losing control and driving into a wall).

► Function of Prepositions in Phrasal Verbs.  In the above example, "drive in" is a phrasal verb – a combination of verb + preposition in which the preposition is more an extension of the meaning of the verb than a standalone preposition.  As a part of speech, it is still a preposition, but we understand it more as a part of the verb.  For instance, in "You should look over your work," the phrasal verb look over means "review."  On the other hand, in "He looked over her shoulder," look over is not a phrasal verb; this does not mean that he reviewed her shoulder because over is used here as a standalone preposition.  Another example:  "She went through [phrasal verb] a crisis" means "She endured a crisis," but "She went through [standalone preposition] a tunnel" does not mean "She endured a tunnel."

Types and Functions of Conjunctions

Coordinating conjunctions link words, phrases, or clauses of equal weight.  The coordinating conjunctions are for, and, nor, but, or, yet, so.  (Some people remember them with the mnemonic device "fanboys" – a word created by using the first letter in each of these conjunctions.)

Coordinators may link two words:  "Mary and Beth are close friends" (and connects two subjects, forming a compound subject).  They may link two clauses:  "Mary and Beth are close friends, but they don't always agree" (but connects two independent clauses, forming a compound sentence).  They may link two phrases:  "Mary and Beth are close friends, but they don't always agree about where to go or what to do" (or connects the two phrases "where to go" and "what to do").

Subordinating conjunctions introduce adverb clauses and thus connect the sentence's independent (main) clause to a dependent (subordinate) clause to form a complex sentence.   Among the words that function as subordinating conjunctions are although, because, if, when, whenever, since, after, before, and while.

Because subordinating conjunctions introduce dependent clauses, they are fixed at the beginning of the clause.  The previous sentence begins with a dependent clause introduced by the subordinating conjunction because.  Here's one in which the dependent clause comes after the main clause:  "I will go with you if you will drive" (the subordinating conjunction if introduces the dependent clause "if you will drive").

► For more about the function of coordinating and subordinating conjunctions in compound and complex sentences, see this site's article on Sentence Patterns.

Correlative conjunctions are always used in pairs.  Among the most common correlatives are  either . . . or, neither . . . nor, not only . . . but also, both . . . and, just as . . . so, and whether . . . or.  Like coordinating conjunctions, correlative conjunctions link items of equal weight.  Examples:  "Just as a musician needs to practice music, so a writer needs to practice writing" (the correlatives link two clauses).  "Neither the students nor the teachers want to work on their vacation" (the correlatives link two nouns).

Everything You Need to Know About Interjections

As stated above, interjections are words (Ah! Oh! Wow!) and sometimes short phrases (My god! Good grief!) used to exclaim.  While interjections may be appropriate in informal writing, speech, or reporting dialogue, they are rarely appropriate or necessary in formal writing.  There are many more effective ways to emphasize a point.

Special Consideration:  Verbs That Do Not Function As Verbs
(See also "Those Pesky Verbals" on this website.)

Verbals are verb forms that function as nouns, adjectives, or adverbs.  Because these verbals look like verbs but function as something else, students are often confused by them.  For example, in the sentence, "Good writing is difficult," students are likely to say that writing is a verb.  However, in this sentence, writing refers to the act or task of writing.  It functions as the subject of the sentence (the verb in this sentence is simply is); therefore, what looks like a verb is playing the part of a noun.  Similarly, in the sentence, "She took a writing course," writing does not function as a verb but as an adjective – it tells what kind of course she took and is therefore used as a modifier of the noun course (the verb in this sentence is took).  On the other hand, in the sentence, "She is writing," writing is a verb; in combination with the auxiliary verb is, it tells what she is doing (it describes an action).

Since part of speech is determined by how a word functions in a sentence, it's important to recognize when what looks like a verb is not functioning as a verb.  That's why it is important to recognize verbals and even more important to understand how they work.  We distinguish three types of verbals – participles, gerunds, and infinitives.

►  Participles.  As we have seen, virtually every verb has a present participle (ending in -ing, such as writing or learning) and a past participle (which ends in -d or -ed, such as learned, or is formed irregularly, such as written).  When the participle is used with an auxiliary verb, such as is or has, it does function as a verb:  is writing, has written, were learning, had learned.  However, the participial form of the verb is often used as a modifier (almost always an adjective), and the present participle may be used as a noun (see "Gerunds" below).

Examples
> "This is a frustrating job."  Frustrating, the present participle of the verb frustrate, functions as an adjective, modifying the noun job.
> "Please submit a written report."  The past participle of the verb write (written) is used to modify the noun report.
> "The injured driver was intoxicated."  The past participles injured and intoxicated (from the verbs injure and intoxicate) both modify the noun driver.
> "Quit your lying ways."  Lying, the present participle of lie, modifies the noun ways.

►  Gerunds.  Gerunds are always used as nouns, and, like present participles, they end in -ing.  One way of looking at gerunds is that they describe the act itself rather than the process of performing the action (as verbs do).

Examples
> "Walking is good exercise."  Walking is a gerund.  It functions as a noun and is the subject of the sentence.  It refers to the act of walking.  (Contrast this to "He is walking in the woods," in which walking is used as a verb.)
> "Maria enjoys skiing."  Skiing is a gerund, functioning as a noun, the object of the verb enjoys.  It tells what Maria enjoys.

►  Infinitives.  An infinitive consists of the base form of the verb preceded by to:  to die, to sleep, to dream.  An infinitive may be used as a noun, adjective, or adverb.

Examples
> "Rich likes to drink coffee."  The infinitive to drink is used as a noun, the direct object of the verb likes.  (The noun coffee is, in turn, said to be the object of the infinitive; to drink coffee constitutes an infinitive phrase.)
> "Bar Harbor is the place to go for summer fun."  The infinitive to go is used as an adjective; it modifies the noun place.
> "She went to the mall to look for shoes."  The infinitive to look is used as an adverb.  It modifies the verb went by telling why she went.

SOURCES.  These are the primary sources used in the preparation of this page –

Aaron, Jane E.  LB Brief.  [Brief edition of The Little, Brown Handbook]  New York: Pearson, 2002.

Kirszner, Laurie G. and Stephen R. Mandell.  The Brief Holt Handbook.  3rd ed.  Fort Worth: Harcourt, 2001.