HESI A2 Grammar Section: 15 Common Mistakes That Cost Students Points [2026]

The HESI A2 Grammar section is one of the most underestimated parts of the exam. Many nursing students assume their everyday English skills will carry them through — only to lose critical points on tricky questions about subject-verb agreement, comma splices, and commonly confused words. In this guide, we break down the 15 most common grammar mistakes students make and show you exactly how to avoid them.

What the HESI A2 Grammar Section Tests

The Grammar section evaluates your understanding of standard written English. You'll encounter 50 questions covering:

• Parts of speech — nouns, pronouns, verbs, adjectives, adverbs, conjunctions, prepositions
• Sentence structure — fragments, run-ons, comma splices, parallel structure
• Subject-verb agreement — matching singular/plural subjects with correct verb forms
• Pronoun-antecedent agreement — ensuring pronouns match their referents
• Punctuation — commas, semicolons, colons, apostrophes
• Commonly confused words — affect/effect, their/there/they're, then/than

Mistake #1: Ignoring Subject-Verb Agreement with Prepositional Phrases

One of the most frequently tested concepts is subject-verb agreement when a prepositional phrase separates the subject from its verb. The trick is that the object of the preposition is never the subject.

Wrong: "The box of medical supplies were delivered."
Right: "The box of medical supplies was delivered."

The subject is "box" (singular), not "supplies." Always mentally remove the prepositional phrase to find the true subject.

Mistake #2: Confusing "Affect" and "Effect"

This pair appears on nearly every HESI A2 exam. Here's the simplest rule:

• Affect = verb (to influence). "The medication may affect your appetite."
• Effect = noun (a result). "The effect of the drug was immediate."

Memory trick: Affect = Action (verb), Effect = End result (noun).

Mistake #3: Creating Comma Splices

A comma splice joins two independent clauses with only a comma — and it's always wrong.

Wrong: "The patient was discharged, she felt much better."
Right: "The patient was discharged; she felt much better." (semicolon)
Also right: "The patient was discharged, and she felt much better." (comma + conjunction)

Mistake #4: Misusing "Their," "There," and "They're"

These homophones are tested constantly:

• Their = possessive ("Their vital signs are stable.")
• There = location/existence ("There is a new policy.")
• They're = they are ("They're preparing for the procedure.")

Mistake #5: Dangling Modifiers

A dangling modifier describes something not clearly stated in the sentence.

Wrong: "After reviewing the chart, the medication was administered."
(Who reviewed the chart? The medication?)
Right: "After reviewing the chart, the nurse administered the medication."

Mistake #6: Using "Less" When You Mean "Fewer"

Use "fewer" for things you can count and "less" for things you cannot.

Wrong: "The patient had less complications."
Right: "The patient had fewer complications."

Mistake #7: Pronoun Case Errors

Choosing between "I/me," "who/whom," and "he/him" trips up many test-takers.

Quick test: Remove the other person from the sentence. "The doctor spoke to Maria and (I/me)" → "The doctor spoke to me" → correct answer is "me."

Mistake #8: Run-On Sentences

Two independent clauses smashed together without any punctuation or conjunction create a run-on.

Wrong: "The lab results were abnormal the doctor ordered more tests."
Right: "The lab results were abnormal, so the doctor ordered more tests."

Mistake #9: Misplacing Apostrophes

Remember: apostrophes show possession or contraction — never plurals.

• "It's" = it is. "Its" = possessive.
• "Nurses'" = belonging to multiple nurses. "Nurse's" = belonging to one nurse.

Mistake #10: Faulty Parallel Structure

Items in a list or comparison must follow the same grammatical pattern.

Wrong: "The nurse enjoys patient care, teaching, and to do research."
Right: "The nurse enjoys patient care, teaching, and research."

Mistake #11: Confusing "Then" and "Than"

• Then = time sequence ("First take vitals, then administer meds.")
• Than = comparison ("Her blood pressure is higher than normal.")

Mistake #12: Using "Which" Instead of "That"

"That" introduces essential clauses (no comma). "Which" introduces non-essential clauses (with comma).

Example: "The medication that was prescribed is effective." vs. "The medication, which was prescribed yesterday, is effective."

Mistake #13: Double Negatives

Wrong: "The patient doesn't have no allergies."
Right: "The patient doesn't have any allergies." or "The patient has no allergies."

Mistake #14: Incorrect Verb Tense Shifts

Don't switch tenses mid-sentence or mid-paragraph without reason.

Wrong: "The nurse assessed the patient and then explains the diagnosis."
Right: "The nurse assessed the patient and then explained the diagnosis."

Mistake #15: Sentence Fragments

A sentence must have a subject, a verb, and express a complete thought.

Fragment: "Because the patient was non-compliant."
Complete: "The treatment failed because the patient was non-compliant."

Quick-Reference Grammar Cheat Sheet

How to Study Grammar Effectively

Grammar isn't about memorizing thousands of rules — it's about recognizing patterns. Here's your study plan:

1. Week 1: Focus on the 5 most common errors (subject-verb agreement, affect/effect, comma splices, homophones, modifiers)
2. Week 2: Master punctuation rules (apostrophes, semicolons, colons)
3. Week 3: Practice with full-length grammar sections using timed conditions
4. Week 4: Review missed questions and drill weak areas

Our practice tests include grammar-focused questions that mirror the real exam format. Combined with our flashcard system, you can master every grammar rule the HESI A2 tests.

Final Tip: Read the Entire Sentence

The HESI A2 grammar questions often include distractors designed to make wrong answers look correct at first glance. Always read the complete sentence, identify the subject and verb, and eliminate obviously wrong choices before selecting your answer.