The HESI A2 Grammar section tests your understanding of Standard Written English — the formal rules that govern academic and professional writing. Unlike everyday speech, the exam expects precise grammar, and even strong students lose points on tricky rules they "sort of" know. This cheat sheet gives you every rule you need, organized by topic, with examples pulled directly from common HESI A2 question patterns.
Bookmark this page and review it the week before your exam. If you can master these rules, you'll be well on your way to scoring 90%+ on the Grammar section.
📋 Quick Navigation: This guide covers 8 major grammar categories: Subject-Verb Agreement, Pronoun Rules, Comma Rules, Semicolons & Colons, Apostrophes, Commonly Confused Words, Sentence Structure, and Adjective/Adverb Usage.
1. Subject-Verb Agreement
The #1 most-tested grammar concept on the HESI A2. The rule is simple: singular subjects take singular verbs; plural subjects take plural verbs. The difficulty comes from sentences designed to confuse you about which word is the actual subject.
Rule 1: Ignore Prepositional Phrases Between Subject and Verb
The subject is never inside a prepositional phrase. Cross out the phrase and match the verb to the true subject.
- ✅ The box of surgical instruments is sterile. (Subject = box, singular)
- ❌ The box of surgical instruments are sterile.
- ✅ The results of the blood test were inconclusive. (Subject = results, plural)
Rule 2: Compound Subjects with "And" Are Plural
- ✅ The nurse and the physician were reviewing the chart.
- Exception: When the compound subject refers to a single entity: "Macaroni and cheese is served in the cafeteria."
Rule 3: "Or" / "Nor" — Verb Matches the Closer Subject
- ✅ Neither the doctor nor the nurses were available. (nurses = closer, plural)
- ✅ Neither the nurses nor the doctor was available. (doctor = closer, singular)
Rule 4: Indefinite Pronouns
Always singular: each, every, everyone, everybody, anyone, anybody, someone, somebody, nobody, nothing, either, neither
- ✅ Each of the patients has a chart. (NOT "have")
- ✅ Everyone in the waiting rooms is anxious.
Always plural: few, many, several, both
- ✅ Several of the medications require refrigeration.
Depends on the noun they refer to: some, any, all, most, none
- ✅ Some of the water is contaminated. (water = uncountable, singular)
- ✅ Some of the samples are contaminated. (samples = countable, plural)
Rule 5: Collective Nouns
Words like team, staff, committee, family, group are singular when acting as one unit:
- ✅ The nursing staff is meeting at 3 PM.
- ✅ The committee has reached a decision.
2. Pronoun Rules
Rule 6: Pronoun-Antecedent Agreement
A pronoun must agree in number with the noun it replaces (its antecedent).
- ✅ Every student should bring his or her stethoscope. (NOT "their" in formal grammar)
- ✅ The nurses completed their shifts.
Rule 7: Subject vs. Object Pronouns
| Subject (doing the action) | Object (receiving the action) |
|---|---|
| I, he, she, we, they, who | me, him, her, us, them, whom |
- ✅ The award was given to my colleague and me. (NOT "I" — object of preposition)
- ✅ She and I reviewed the lab results. (NOT "her and me" — subjects)
- Trick: Remove the other person — "The award was given to me" sounds right; "The award was given to I" doesn't.
Rule 8: Who vs. Whom
- Who = subject (replace with "he/she"): "Who is calling?" → "He is calling." ✅
- Whom = object (replace with "him/her"): "To whom was the letter sent?" → "The letter was sent to him." ✅
Rule 9: Ambiguous Pronoun Reference
A pronoun must clearly refer to one specific noun.
- ❌ When the nurse spoke to the patient, she was confused. (Who was confused?)
- ✅ The patient was confused when the nurse spoke to her.
3. Comma Rules
Commas are heavily tested. Memorize these patterns:
Rule 10: Commas in a Series (Oxford Comma)
- ✅ The kit contained gauze, tape, and scissors.
- The HESI A2 generally expects the Oxford comma (the comma before "and").
Rule 11: Comma After Introductory Elements
- ✅ After the surgery, the patient was moved to recovery.
- ✅ However, the results were normal.
- ✅ Running behind schedule, the nurse skipped her break.
Rule 12: Commas with Coordinating Conjunctions (FANBOYS)
Use a comma before a coordinating conjunction (For, And, Nor, But, Or, Yet, So) that joins two independent clauses.
- ✅ The patient was stable, but the doctor ordered additional tests.
- ❌ The patient was stable, and alert. (No comma — "alert" is NOT an independent clause)
Rule 13: Commas with Nonessential (Nonrestrictive) Clauses
- ✅ Dr. Smith, who specializes in cardiology, will see the patient. (Nonessential — the name already identifies the doctor)
- ✅ The doctor who specializes in cardiology will see the patient. (Essential — no commas, because it tells us WHICH doctor)
Rule 14: Commas with Appositives
- ✅ Florence Nightingale, the founder of modern nursing, was born in 1820.
4. Semicolons & Colons
Rule 15: Semicolons Join Two Related Independent Clauses
- ✅ The patient's vitals improved; the physician decided to discharge her.
- Both sides of the semicolon must be complete sentences.
Rule 16: Semicolons with Conjunctive Adverbs
Words like however, therefore, moreover, furthermore, nevertheless, consequently:
- ✅ The medication was effective; however, it caused drowsiness.
- ❌ The medication was effective, however, it caused drowsiness. (This creates a comma splice!)
Rule 17: Colons Introduce Lists, Explanations, or Elaborations
- ✅ The exam covers three subjects: math, grammar, and reading.
- Key rule: A complete sentence must come before the colon.
- ❌ The subjects are: math, grammar, and reading. (Incorrect — "The subjects are" doesn't complete the thought)
5. Apostrophes & Possession
Rule 18: Singular Possessive — Add 's
- ✅ The nurse's station (one nurse)
- ✅ James's diagnosis (even if the name ends in "s")
Rule 19: Plural Possessive — Add ' After the s
- ✅ The patients' records (multiple patients)
- ✅ The nurses' lounge (multiple nurses)
Rule 20: It's vs. Its
- It's = it is / it has ("It's important to wash hands.")
- Its = possessive ("The hospital updated its policy.") — NO apostrophe!
6. Commonly Confused Words
The HESI A2 loves testing these pairs. Memorize the differences:
| Word | Meaning | Example |
|---|---|---|
| affect | verb — to influence | The drug affects heart rate. |
| effect | noun — a result | The effect was immediate. |
| than | comparison | Aspirin is cheaper than ibuprofen. |
| then | time/sequence | Take vitals, then administer meds. |
| their | possessive | Patients should bring their ID. |
| there | location/existence | There are 50 beds on this floor. |
| they're | they are | They're discharging the patient. |
| your | possessive | Check your patient's chart. |
| you're | you are | You're scheduled for the night shift. |
| accept | to receive | The hospital accepts most insurance. |
| except | to exclude | All labs are normal except glucose. |
| lie | to recline (no object) | The patient should lie down. |
| lay | to place (needs object) | Lay the instruments on the tray. |
7. Sentence Structure Errors
Rule 21: Sentence Fragments
A sentence must have a subject + verb + complete thought.
- ❌ "Because the patient was discharged early." (Fragment — dependent clause with no main clause)
- ✅ "The bed was cleaned because the patient was discharged early."
Rule 22: Run-On Sentences & Comma Splices
Two independent clauses cannot be joined by just a comma or nothing at all.
- ❌ "The patient improved, the doctor discharged her." (Comma splice)
- ❌ "The patient improved the doctor discharged her." (Run-on / fused sentence)
Fix with any of these:
- Period: "The patient improved. The doctor discharged her."
- Semicolon: "The patient improved; the doctor discharged her."
- Coordinating conjunction: "The patient improved, so the doctor discharged her."
- Subordination: "Because the patient improved, the doctor discharged her."
Rule 23: Parallel Structure
Items in a list or comparison must follow the same grammatical form.
- ❌ The nurse is responsible for assessing patients, administering medications, and to document care.
- ✅ The nurse is responsible for assessing patients, administering medications, and documenting care.
Rule 24: Misplaced and Dangling Modifiers
- ❌ Running a high fever, the nurse administered Tylenol. (Was the NURSE running a fever?)
- ✅ Running a high fever, the patient was given Tylenol by the nurse.
- ✅ The nurse administered Tylenol to the patient, who was running a high fever.
8. Adjective & Adverb Usage
Rule 25: Adjectives Modify Nouns; Adverbs Modify Verbs/Adjectives/Other Adverbs
- ✅ The patient recovered quickly. (Adverb modifying "recovered")
- ❌ The patient recovered quick.
- ✅ The wound looked bad. (Adjective after linking verb "looked")
- ❌ The wound looked badly. (This would mean the wound has poor eyesight!)
Rule 26: Comparative vs. Superlative
| Form | Comparing | Example |
|---|---|---|
| Comparative (-er / more) | Two items | Drug A is more effective than Drug B. |
| Superlative (-est / most) | Three or more | Drug A is the most effective of the three. |
- ❌ "Between the two treatments, this one is best." (Use "better" for two items)
- ❌ "This is the more effective drug of all five." (Use "most" for 3+)
⚠️ Double Negatives: Avoid using two negative words in the same clause. "The patient didn't feel nothing" is incorrect — it should be "The patient didn't feel anything" or "The patient felt nothing."
Quick-Reference Cheat Sheet
🟢 Top 10 Rules to Memorize (Most Frequently Tested):
- Cross out prepositional phrases to find the true subject
- "Each/every/everyone" is ALWAYS singular
- Use a comma + FANBOYS to join independent clauses
- Semicolons join two complete sentences (no conjunction needed)
- It's = it is; Its = possessive
- Affect = verb; Effect = noun
- Parallel structure in lists (all -ing, all to+verb, or all nouns)
- Modifiers must be next to the word they describe
- Comparative = 2 things; Superlative = 3+ things
- Remove the other person to check subject/object pronouns
How to Study These Rules for Maximum Retention
- Read through the full list once — highlight any rules that surprised you
- Take practice questions — after each one, identify WHICH rule was being tested
- Make flashcards for the rules you keep getting wrong
- Review this cheat sheet 3 days, 1 day, and 1 hour before your exam
- Trust the rules over your ear — spoken English often violates formal grammar rules
🎯 Ready to Test Your Grammar Knowledge? Our practice tests include realistic HESI A2 grammar questions that test every rule on this page. Take a free practice test →