Identify parts of speech and their functions

SECTION 1

Historical Context & Motivation

The classification of words into distinct grammatical categories is one of the oldest intellectual endeavors in Western and Eastern scholarship alike. Long before modern linguistics formalized syntax and morphology as separate disciplines, ancient grammarians recognized that words in a sentence serve fundamentally different roles—some denote actions, others name entities, and still others modify or connect those elements. Understanding the parts of speech is not merely an academic exercise; for graduate-level test takers preparing for the HESI A2 Grammar section, it constitutes the foundational framework upon which every question about sentence structure, agreement, and word choice ultimately rests. A misidentified part of speech cascades into errors in subject-verb agreement, pronoun reference, modifier placement, and parallelism—all of which the HESI A2 tests with precision.

~100 BCE

Dionysius Thrax's Technē Grammatikē

The earliest surviving Greek grammar text codified eight parts of speech (noun, verb, participle, article, pronoun, preposition, adverb, conjunction), establishing a taxonomy still recognizable today.

~500 CE

Priscian's Institutiones Grammaticae

The Roman grammarian Priscian adapted the Greek system for Latin, replacing the article (absent in Latin) with the interjection, producing the eight-part system that dominated European education for over a millennium.

1762

Robert Lowth's A Short Introduction to English Grammar

Lowth formalized prescriptive English grammar rules, cementing the eight traditional parts of speech—noun, pronoun, verb, adjective, adverb, preposition, conjunction, interjection—as the standard framework for English instruction.

1957

Chomsky's Syntactic Structures

Noam Chomsky's generative grammar reframed parts of speech as phrase-structure categories within hierarchical trees, deepening the theoretical understanding of how word classes function within sentences.

Present

Standardized Exam Applications

Exams such as the HESI A2 rely on the traditional eight-part framework to assess grammatical competence, requiring test takers to identify word functions within context-dependent sentences.

The central question this lesson addresses is deceptively simple: given any word in a sentence, how do you determine which part of speech it is, and what syntactic function does it perform? Because English is a relatively analytic language—relying on word order and function words rather than extensive inflectional morphology—the same word form can often serve as multiple parts of speech depending on context. The word run may be a verb ("She runs daily"), a noun ("a morning run"), or an adjective ("run-down building"). Mastering this contextual identification is precisely what the HESI A2 Grammar section demands.

SECTION 2

Core Principles & Definitions

Before examining each part of speech individually, it is essential to internalize the overarching principles that govern how words are classified. A part of speech is a category to which a word is assigned based on its syntactic function—what it does in a sentence—rather than its inherent meaning alone. This functional definition is critical: the same lexical item may belong to different categories in different sentences. The following foundational ideas structure the entire system.

Form vs. Function

A word's form (its morphological shape—suffixes, inflections) provides clues, but its function (the role it plays in its clause) is the definitive criterion. The suffix -ly often signals an adverb, but friendly is an adjective.

Open vs. Closed Classes

Open-class words (nouns, verbs, adjectives, adverbs) readily admit new members through coinage and borrowing. Closed-class words (pronouns, prepositions, conjunctions, interjections) form a relatively fixed inventory that changes only over centuries.

Content vs. Function Words

Content words carry lexical meaning (nouns, verbs, adjectives, adverbs). Function words serve grammatical purposes, signaling relationships between content words (prepositions, conjunctions, articles, auxiliary verbs).

Context Determines Category

English allows extensive conversion (also called zero derivation): a word may shift categories without any morphological change. "I water the plants" (verb) vs. "the water is cold" (noun). Always analyze in context.

Hierarchical Sentence Structure

Words combine into phrases, which combine into clauses. Identifying the part of speech of a word often requires determining which phrase it heads or modifies, and what role that phrase plays in the larger clause.

✦ KEY TAKEAWAY

Think of the eight parts of speech as a casting system for a play. Each word is an actor, and its part of speech is the role it plays in a given scene (sentence). The same actor can play the lead (noun/subject) in one scene and a supporting role (adjective/modifier) in another. Just as a director assigns roles based on what the scene requires, a sentence's structure assigns parts of speech based on syntactic need. When the HESI A2 asks you to identify a part of speech, it is asking: what role is this word playing right now?

SECTION 3

Visual Overview of the Eight Parts of Speech

The following diagram presents the eight traditional parts of speech arranged into two tiers: the four open-class (content) words on the left and the four closed-class (function) words on the right. Each category is annotated with its primary syntactic function and a concise example. This visual taxonomy serves as a reference map throughout the lesson.

Figure 1 — The eight traditional parts of speech divided into open-class content words (left, cyan border grouping) and closed-class function words (right, pink border grouping). Each card lists the primary syntactic function and a healthcare-context example.

As the diagram illustrates, the open-class categories on the left constitute the bulk of vocabulary in any sentence. Every sentence requires at least a verb (the predicate), and most require a noun or pronoun as the subject. Adjectives and adverbs add descriptive precision, while the closed-class words on the right provide the grammatical scaffolding—linking ideas (conjunctions), situating entities in space and time (prepositions), avoiding repetition (pronouns), and expressing emotional reactions (interjections). When tackling a HESI A2 question, begin by locating the verb and subject, then work outward to classify the remaining words.

SECTION 4

How Parts of Speech Function in Sentence Architecture

Understanding parts of speech requires recognizing how each category interacts with the others to produce grammatically coherent sentences. English sentences are built from phrases—groups of related words centered on a head word—which in turn combine into clauses. The part of speech of the head word determines the phrase type: a noun heads a noun phrase (NP), a verb heads a verb phrase (VP), a preposition heads a prepositional phrase (PP), and so forth. This hierarchical organization is the mechanism by which parts of speech produce meaning.

Syntactic Slots and Their Expected Parts of Speech

Syntactic slots and the parts of speech that typically fill them

Syntactic Slot	Expected Part of Speech	Example
Subject	Noun or Pronoun	The physician ordered labs.
Predicate	Verb (finite)	The physician ordered labs.
Direct Object	Noun or Pronoun	The physician ordered labs.
Subject Complement	Adjective or Noun	The patient is stable.
Adverbial Modifier	Adverb or PP	She spoke calmly / with confidence.
Attributive Modifier	Adjective	The acute infection spread.

Diagnostic Tests for Identifying Parts of Speech

The substitution test: Replace the word with a prototypical member of a category. If 'it' or 'something' can replace the word and the sentence remains grammatical, the word is likely a noun or pronoun.
The modification test: If the word can be modified by 'very,' it is likely an adjective or adverb. If it can take a determiner ('the,' 'a'), it is functioning as a noun.
The inflection test: If the word can be inflected for tense (walked, walking), it is a verb. If it can take plural or possessive markers (-s, -'s), it is a noun.
The position test: Consider where the word appears in the sentence. Words between a determiner and a noun typically function as adjectives; words immediately following a verb that modify it function as adverbs.

💡 HESI A2 Strategy

When the HESI A2 presents a sentence and asks you to identify the part of speech of a particular word, apply the diagnostic tests in sequence: first try substitution, then check what modifies the word or what it modifies, and finally consider its position relative to known sentence elements. This systematic approach prevents the common error of classifying by appearance rather than function.

SECTION 5

Detailed Breakdown of Each Part of Speech

This section provides a systematic examination of each of the eight parts of speech, with particular attention to subtypes and boundary cases that frequently appear on the HESI A2 exam. Understanding these nuances will equip you to handle even the most deceptive distractor options.

Figure 2 — A parse tree decomposing the sentence "The experienced nurse carefully administered the intravenous medication" into its constituent phrases and individual parts of speech. Note how the adjective experienced modifies the noun nurse within the subject NP, while the adverb carefully modifies the verb administered within the predicate VP.

Nouns: Subtypes and Functions

Nouns name people, places, things, or abstract concepts. On the HESI A2, you should be able to distinguish common nouns (patient, hospital) from proper nouns (Mayo Clinic, Dr. Rodriguez), concrete nouns (syringe, thermometer) from abstract nouns (diagnosis, empathy), and collective nouns (staff, team) from individual count nouns. Functionally, nouns serve as subjects, direct objects, indirect objects, objects of prepositions, and subject or object complements. A critical HESI pattern involves gerunds—verb forms ending in -ing that function as nouns: "Swimming strengthens cardiovascular endurance."

Verbs: Action, Linking, and Helping

Verbs constitute the predicate core and divide into three functional categories. Action verbs express physical or mental activity (administer, diagnose, consider). Linking verbs (is, seems, appears, becomes) connect the subject to a complement that renames or describes it—after a linking verb, the complement is typically a predicate adjective or predicate nominative, not a direct object. Helping (auxiliary) verbs (has, will, can, should, is) combine with a main verb to form verb phrases that express tense, mood, or voice. The HESI A2 frequently tests whether a word is functioning as a main verb or an auxiliary: in "She has completed the assessment," has is an auxiliary, while completed is the main verb.

Adjectives, Adverbs, and the Modification Hierarchy

Adjectives modify nouns and pronouns, appearing in two positions: attributive (before the noun: "the sterile bandage") and predicative (after a linking verb: "the bandage is sterile"). Adverbs modify verbs, adjectives, or other adverbs, answering how, when, where, or to what degree. While many adverbs end in -ly (quickly, thoroughly), many common adverbs do not: very, often, never, here, soon, well. The HESI A2 commonly presents adjective-adverb confusion ("She did good" vs. "She did well") as a test item.

Prepositions, Conjunctions, Pronouns, and Interjections

Prepositions (in, on, at, by, with, during, between) introduce prepositional phrases that function as adjectives or adverbs. Conjunctions come in three varieties: coordinating (FANBOYS: for, and, nor, but, or, yet, so), subordinating (because, although, when, if, since), and correlative (both…and, either…or, neither…nor). Pronouns replace nouns and include personal (I, she, they), possessive (my, hers), reflexive (myself, themselves), relative (who, which, that), demonstrative (this, those), and indefinite (everyone, somebody) subtypes—each subject to its own agreement and case rules. Interjections (oh, wow, alas) are grammatically independent expressions of emotion and appear least frequently on the HESI A2, though they may serve as distractors.

SECTION 6

Worked Example: Identifying Every Part of Speech

Consider the following sentence, representative of HESI A2 complexity: "Ouch! The new intern quickly but carefully bandaged the deep laceration on his forearm." We will systematically identify each word's part of speech and explain its syntactic function.

Full Sentence Parse

Step 1 — Identify the InterjectionThe word "Ouch!" stands alone, separated by an exclamation point. It expresses a sudden emotion (pain) and has no grammatical connection to the main clause. It is an interjection.

Ouch = interjection

Step 2 — Locate the Main VerbScanning the main clause, identify the action: who did what? Someone bandaged something. The word bandaged is in past tense (inflected with -ed), expressing a physical action. It is the main verb and forms the predicate core. Note that bandage can also be a noun, but here its inflection for tense and its position after adverbs confirm its verbal function.

bandaged = verb (action, past tense, transitive)

Step 3 — Identify the Subject Noun PhraseWho bandaged? "The new intern" is the subject NP. The is a definite article functioning as an adjective (it modifies intern by specifying which one). New is a descriptive adjective in attributive position (before the noun). Intern is a common noun functioning as the subject.

The = adjective (article) | new = adjective | intern = noun (subject)

Step 4 — Classify the Adverbs and ConjunctionThe words "quickly" and "carefully" both modify the verb bandaged, telling how the action was performed. Both end in -ly and pass the modification test. They are adverbs of manner. The word "but" connects these two adverbs as equal elements, making it a coordinating conjunction (one of the FANBOYS).

quickly = adverb | but = conjunction | carefully = adverb

Step 5 — Parse the Object NP and Prepositional PhraseThe intern bandaged what? "the deep laceration" is the direct object NP. The = adjective (article), deep = adjective (attributive), laceration = noun (direct object). The phrase "on his forearm" is a prepositional phrase modifying laceration (telling where the laceration is), so it functions adjectivally. On = preposition, his = possessive pronoun (functioning adjectivally to modify forearm), forearm = noun (object of the preposition).

✓ Result Summary

All eight parts of speech are present in this single sentence: interjection (Ouch), adjective (The, new, the, deep), noun (intern, laceration, forearm), adverb (quickly, carefully), conjunction (but), verb (bandaged), preposition (on), pronoun (his). This demonstrates that even a moderately complex sentence can contain all eight categories.

SECTION 7

Common Pitfalls & Tricky Cases on the HESI A2

The HESI A2 Grammar section is designed to distinguish test takers who identify parts of speech by rote from those who analyze function in context. The following table presents the most frequently tested pitfalls—cases where surface appearance misleads and only functional analysis yields the correct answer.

Common part-of-speech confusion points on the HESI A2 Grammar section

Pitfall / Confusion	Why It's Tricky	How to Resolve
Gerund vs. Present Participle	Both end in -ing. "Running is healthy" (gerund = noun) vs. "The running water" (participle = adjective) vs. "She is running" (participle in progressive verb phrase).	Apply the substitution test: if you can replace the -ing word with a noun ("Exercise is healthy"), it is a gerund. If it modifies a noun, it is a participial adjective. If it follows a helping verb, it is part of the verb phrase.
Adjective vs. Adverb	"She feels bad" (adjective after linking verb) vs. "She performed badly" (adverb modifying action verb). Not all adverbs end in -ly; not all -ly words are adverbs (lovely, friendly).	Determine what the word modifies. If it modifies a noun/pronoun (including after a linking verb), it is an adjective. If it modifies a verb, adjective, or adverb, it is an adverb.
Possessive Pronoun vs. Adjective	"His chart" — is "his" a pronoun or an adjective? Technically a possessive pronoun, but it functions attributively like an adjective. The HESI A2 typically classifies it as a pronoun.	Follow the test's convention: words like my, your, his, her, its, our, their are classified as pronouns (possessive pronouns) on the HESI A2, even though some grammars call them possessive adjectives.
Preposition vs. Adverb	"She walked in" (adverb — no object follows) vs. "She walked in the room" (preposition — object follows). Same word, different function.	If the word is followed by a noun/pronoun (its object), it is a preposition heading a PP. If it stands alone modifying the verb, it is an adverb.
Noun used as Adjective (Noun Adjunct)	"The hospital room" — "hospital" is a noun by nature but modifies "room" attributively. Is it an adjective?	On the HESI A2, noun adjuncts are generally still classified as nouns. The test focuses on the word's inherent category. However, if asked about function, note it is performing an adjectival role.

🎯 EXAM STRATEGY

Think of identifying parts of speech the way a radiologist reads an image: the same anatomical structure can appear differently depending on the imaging angle (context). A radiologist does not label a structure by its appearance alone but by its position, connections, and function relative to surrounding structures. Similarly, never classify a word by its surface form alone. Ask: what does this word modify, what modifies it, and what syntactic slot does it fill? These relational questions will guide you to the correct classification every time.

SECTION 8

Connection to Advanced Grammar Concepts

While the HESI A2 tests the traditional eight-part-of-speech framework, understanding how this system connects to more advanced grammatical analysis can deepen your comprehension and improve your ability to handle nuanced questions. Modern linguistics often expands or refines the traditional categories, and awareness of these refinements provides an intellectual scaffold that makes the traditional system more intuitive.

Traditional vs. advanced approaches to parts of speech

Traditional Category	Advanced / Expanded View	HESI A2 Relevance
8 parts of speech	Modern grammars identify 10+ categories (adding determiners, particles, auxiliaries as separate classes)	HESI A2 uses the traditional 8-part system; articles are classified as adjectives, auxiliaries as verbs.
Parts of speech (word-level)	Phrase-level analysis: NP, VP, AdjP, AdvP, PP — phrases inherit the category of their head word	HESI A2 may ask about prepositional phrases functioning as adjectives or adverbs; understanding phrase structure helps.
Static classification	Functional grammar: the same word analyzed by its discourse role (Theme, Rheme) and transitivity (Actor, Goal)	Not directly tested, but the principle that function > form aligns with the HESI's emphasis on contextual identification.
Prescriptive rules	Descriptive linguistics: actual usage data, corpus analysis, register variation	HESI A2 adheres to prescriptive Standard American English. Know the prescribed rules even when descriptive usage may differ.

For your HESI A2 preparation, the practical takeaway is straightforward: master the traditional eight-part system and the diagnostic tests outlined in Section 4. However, if you encounter an ambiguous question—especially one involving phrases functioning as different parts of speech—the phrase-level analysis from modern grammar provides an additional reasoning tool. For instance, recognizing that the entire prepositional phrase "in the emergency room" functions adverbially (modifying a verb to indicate where) or adjectivally (modifying a noun to specify which one) is precisely the kind of higher-order analysis that distinguishes top scorers.

SECTION 9

Practice Problems

The following five problems mirror the style and difficulty of HESI A2 Grammar questions. Work through each one by applying the diagnostic tests and contextual analysis discussed throughout this lesson.

PROBLEM 1 — CONCEPTUAL

In the sentence "The diagnosis surprised everyone," what part of speech is the word diagnosis, and what is its syntactic function?

PROBLEM 2 — BASIC CALCULATION

Identify the part of speech of the word rapidly in: "The patient's condition deteriorated rapidly after surgery."

PROBLEM 3 — INTERMEDIATE

In the sentence "Running five miles every morning keeps her cardiovascular system strong," identify the part of speech and function of (a) running and (b) strong.

PROBLEM 4 — APPLIED

Consider: "Although the surgeon operated skillfully, the outcome was neither favorable nor expected." Identify the part of speech of each of the following: (a) although, (b) skillfully, (c) neither…nor, (d) expected.

PROBLEM 5 — CRITICAL THINKING

In the sentence "The well water tested well," explain the part of speech and function of each instance of well. Then discuss how the same word form can belong to different parts of speech and what principle of English grammar this illustrates.

SUMMARY

Lesson Summary

The English language organizes words into eight traditional parts of speech: nouns (name entities and serve as subjects, objects, or complements), verbs (express action or state of being and form the predicate core), adjectives (modify nouns in attributive or predicative position), adverbs (modify verbs, adjectives, or other adverbs), pronouns (replace nouns to avoid repetition), prepositions (head phrases showing spatial, temporal, or logical relationships), conjunctions (connect words, phrases, or clauses as coordinating, subordinating, or correlative types), and interjections (grammatically independent expressions of emotion).

The decisive principle for the HESI A2 is that context determines classification: the same word form can function as different parts of speech depending on its syntactic position and relationships. Apply the four diagnostic tests—substitution, modification, inflection, and position—to resolve ambiguous cases. Remember the distinction between open-class content words (nouns, verbs, adjectives, adverbs) and closed-class function words (pronouns, prepositions, conjunctions, interjections), and pay particular attention to high-frequency confusion points: gerunds vs. participles, adjective vs. adverb after linking verbs, and prepositions vs. adverbs. Mastering these distinctions equips you not only for the Grammar section but also strengthens your performance on HESI A2 reading comprehension, where syntactic precision enhances interpretive accuracy.