Lesson · G.3.3

Comma and punctuation errors

The HESI A2 Grammar subtest rewards a small set of comma rules applied consistently. Learn where a comma belongs, where it does not, and how to fix a run-on.

ObjectiveG.3.3Read4 minExam weightCommon Errors and Usage ≈ 36% of Grammar

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What you will be able to do

Join two complete sentences with a comma and a coordinating conjunction, a semicolon, or a period, and never with a comma alone.
Place a comma after an opening dependent clause and omit it when the same clause follows the main clause.
Punctuate a series and a nonessential clause correctly, and use apostrophes for possession rather than for plurals.

What the lesson concludes

A comma alone cannot join two independent clauses. That is a comma splice, one form of run-on sentence.
A comma follows a dependent clause that opens a sentence but is dropped when that clause comes at the end.
Use a comma before the final item in a series, and set off nonessential information with commas on both sides.
An apostrophe shows possession or a missing letter. It never makes a word plural.