Section 5.1 Parts of Speech
Most students first learn about parts of speech through definitions based on meaning. You’ve probably heard these:
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A noun names a person, place, thing, or idea.
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A verb is an action word.
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An adjective describes a noun.
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An adverb modifies a verb.
These semantic definitions—definitions based on meaning—are helpful starting points. They work well for many common words: “teacher” names a person (noun), “run” expresses an action (verb), “tall” describes a quality (adjective), “quickly” tells how an action is performed (adverb).
The Limits of Semantic Definitions.
But semantic definitions run into trouble surprisingly often. Consider these challenges:
Is "destruction" a thing? The word “destruction” is clearly a noun—it follows “the” (“the destruction”), it can be plural (“destructions”), and it has a noun suffix (-tion). Yet it doesn’t name a "thing" in any concrete sense. It names an action or event. Similarly, arrival, swimming, development, and happiness are all nouns, but none names a "person, place, or thing."
Is "know" an action? The verb “know” doesn’t describe anything we actively do—it describes a mental state. So do believe, own, resemble, and deserve. These are verbs, but calling them "action words" stretches the definition uncomfortably.
Where do function words fit? What "thing" does “the” name? What action does “is” perform? Words like the, a, of, and very play grammatical roles that semantic definitions cannot easily capture.
The fundamental problem is that semantic definitions work backward: they assume we already know what the word means and then try to fit that meaning into a category. But meaning is slippery, and the same word can mean different things in different contexts.
A Better Approach: Form and Function.
In this course, we’ll use two more reliable methods for identifying parts of speech:
Morphological tests examine what forms a word can take—what endings or inflections it accepts. Nouns can be plural and possessive. Verbs can take past tense and -ing. Adjectives can be compared. These patterns are consistent regardless of meaning.
Syntactic tests examine how a word functions in sentences—where it can appear and what other words can accompany it. Nouns follow determiners like the. Verbs follow modals like can. Adjectives appear between the and a noun.
Together, these tests give us objective criteria for classification. Rather than asking "Does this word name a thing?" (which is debatable), we ask "Can this word be pluralized? Can it follow the?" (which we can test directly).
The Two Questions.
When analyzing any word in a sentence, you must ask two separate questions:
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What IS this word? (form—its part of speech)
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What is this word DOING? (function—its grammatical role)
These questions have different answers, and both answers matter. This is the dual-identification principle, and it will guide your analysis throughout this course.
Form: What a Word IS.
Form refers to a word’s part of speech—its inherent grammatical category. We determine form by examining the word’s morphological properties (what endings it can take) and its typical syntactic behavior.
For example, “happy” is an adjective. How do we know? Because it passes the tests for adjectives:
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It can be compared: happier, happiest
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It can be modified by very: very happy
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It can appear after linking verbs: She seems happy
These properties belong to the word itself, regardless of how it’s used in any particular sentence.
Function: What a Word DOES.
Function refers to the grammatical role a word plays in a specific sentence. The same word can perform different functions in different sentences—and sometimes a word’s function differs from what we’d expect based on its form.
Consider the word “poor”:
“The poor deserve our help.”
What is “poor”? By form, it’s an adjective (it can be graded: poorer, poorest). But what is it doing in this sentence? It’s functioning as a noun—it follows a determiner (the), it serves as the subject of the sentence, and it refers to a group of people. We call this an adjective functioning nominally (doing the job of a noun).
Form and Function Can Match or Differ.
Example 1: Form and function match
“She spoke quietly.”
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Form: quietly is an adverb (formed with -ly from adjective quiet)
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Function: quietly functions adverbially (it modifies the verb spoke, telling us how she spoke)
Here form and function align—an adverb doing adverb work.
Example 2: Form and function differ
“The coffee table needs dusting.”
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Form: coffee is a noun (it can be pluralized: coffees; it can follow determiners: the coffee)
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Function: coffee functions adjectivally (it modifies table, telling us what kind of table)
Here a noun is doing the work typically done by adjectives.
Example 3: Another mismatch
“She runs fast.”
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Form: fast is typically an adjective (a fast car, faster, fastest)
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Function: fast functions adverbially (it modifies runs, telling us how she runs)
Why This Matters.
The form/function distinction matters for three reasons:
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Words are flexible.English allows words to shift between functions freely. Understanding this prevents you from making errors like "That can’t be an adjective because it’s modifying a verb."
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Labels depend on context.You cannot fully describe a word’s grammar without seeing it in a sentence. The word “walk” is a verb in “I walk to school” but a noun in “The walk was pleasant.”
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Complete analysis requires both.Saying “poor” is an adjective in the sentence “The poor deserve help” is incomplete. A full analysis recognizes both what the word is (adjective) and what it’s doing (functioning as a noun).
Throughout this chapter, we’ll examine four major word classes. For each one, you’ll learn both morphological tests (to identify form) and syntactic tests (to analyze function). Keep the dual-identification principle in mind: always identify both what a word is and what it’s doing.
