Punctuation and sentence structure on the Grade 10 ELA MCAS: using commas (in lists, after introductory elements, around nonessential clauses, with coordinating conjunctions), apostrophes (possessives and contractions), and end punctuation correctly, and forming complete sentences (independent and dependent clauses) free of fragments and run-ons, in editing items and the long composition.

What this skill is asking

Punctuation and sentence structure are the conventions that mark where sentences and ideas begin and end, and the Grade 10 ELA MCAS tests them in editing items and scores them in the Standard English Conventions trait of the long composition. The core punctuation rules cover commas (in lists, after introductory elements, around nonessential information, and with coordinating conjunctions joining two complete sentences), apostrophes (possessives and contractions), and end punctuation. The core sentence-structure skill is forming complete sentences from independent and dependent clauses, free of fragments, comma splices, and run-ons. The skill students lose points on is comma misuse (especially the splice) and misjudging where a sentence should end. This page covers the high-frequency punctuation rules and clause structure. The transferable skill is controlling sentence boundaries so writing is clear and correct, in editing and in your own essay.

The high-frequency punctuation rules

The first move is to learn the comma and apostrophe rules the test leans on.

The comma rule that causes the most trouble is the one for joining sentences: a comma alone cannot join two complete sentences (that is a comma splice); you need a comma plus a coordinating conjunction, or a semicolon, or a period. The apostrophe trap is "its" versus "it's": the possessive "its" has no apostrophe, while "it's" always means "it is." Learning these as rules, not by feel, is what lets you both answer an editing item and avoid the error in your own writing.

Clauses, fragments, splices, and run-ons

Recognizing clauses is the master skill here, because once you can tell an independent clause from a dependent one, fragments, splices, and run-ons all become visible. A dependent clause usually starts with a subordinating word (because, although, when, if, since) and leaves you waiting for the rest; an independent clause stands complete. This is the same understanding that powers sentence combining, where you join clauses deliberately for variety, and it directly serves the long composition, where varied, correctly bounded sentences support both the conventions trait and the clarity of your ideas.

Working a punctuation or sentence item

Try this

Q1. What is the difference between a comma splice and a run-on? [Recall]

• Cue. Both wrongly join two independent clauses; a comma splice joins them with only a comma, while a run-on joins them with no punctuation at all. Both are fixed with a comma plus conjunction, a semicolon, or a period.

Q2. Fix this sentence: "The library was quiet we could finally study." [Short explanation]

• Cue. It is a run-on (two independent clauses with no punctuation). Fix it with a period ("The library was quiet. We could finally study."), a semicolon, or a comma plus conjunction ("The library was quiet, so we could finally study.").