EN1 Punctuation & Boundaries

Lesson

Roughly a third of the questions on the English section are decided by one skill: knowing where a sentence ends. Not comma feel, not ear. A boundary question is a yes-or-no test with a procedure, and the procedure works every time.

Independent, dependent, and the splice

An independent clause has a subject and a verb and makes sense alone: the tide went out. A dependent clause has a subject and a verb but opens with a word that leans on something else — because, although, when, if, since, while, after, unless — so because the tide went out is not a sentence. A phrase with no subject-plus-verb at all (walking the dog, a retired welder) is never a sentence either.

• Comma splice: two independent clauses joined by a comma alone. The tide went out, the boats settled into the mud.
• Run-on (fused): two independent clauses with nothing between them.
• Fragment: a period or semicolon dropped where one side cannot stand alone.

Watch the words that look like conjunctions and are not: however, therefore, moreover, then, instead, consequently, in fact. They are adverbs. A comma in front of one still leaves a splice; what you need is a semicolon or a period.

The four legal joins

• Period. Always available between two independent clauses.
• Semicolon. Same job as a period, with a hint that the ideas are related.
• Comma + FANBOYS (for, and, nor, but, or, yet, so). The comma alone is not enough and the conjunction alone is not enough; on the ACT you want both.
• Colon, when the second clause explains, defines or delivers on the first.

Because a period and a semicolon do the same work, a real ACT item will never offer you both in clean form. If you see both, look again — one of them is attached to something that is not a complete sentence.

Colons and dashes

A colon needs a complete sentence in front of it. After that it can introduce a list, a single noun, a quotation or a whole explaining clause. What it may never do is sit between a verb and its object, or after such as, including or consists of.

• Right: The kit holds everything a beginner needs: a rod, a reel and a spool of line.
• Wrong: The kit holds: a rod, a reel and a spool of line. (The kit holds is not a sentence.)

A single dash does the colon's job and is a little louder. A pair of dashes does something a colon cannot do at all: fence off an interruption in the middle of a sentence and then let the sentence continue.

Non-essential elements travel in matched pairs

Extra information dropped into the middle of a sentence takes two commas, two dashes or two parentheses — the same mark on both ends. One comma and one dash is always wrong, and so is opening a pair and never closing it. Use dashes or parentheses instead of commas when the interruption already contains commas of its own.

Test it by lifting the element out. If what remains is a complete, sensible sentence, the element is non-essential and needs its pair. If removing it wrecks the meaning — the students who passed the exam did not have to take the final — it is essential and takes no commas at all.

The four commas the ACT wants you to delete

• Between a subject and its verb. The sound coming from the basement, turned out to be the water heater. No matter how long the subject runs, no comma before the verb.
• Before a preposition. She kept the letters in a shoebox, under the stairs.
• Splitting a compound predicate. One subject, two verbs joined by and — no comma: the town drains the pool and scrubs the tile by hand. The comma belongs there only when a second subject follows, making a second full clause.
• Around an essential element. Commas around who passed the exam would say every student passed.

Apostrophes

• Possession: singular adds 's (the coach's whistle); a plural already ending in s adds only the apostrophe (the coaches' whistles); an irregular plural adds 's (children's).
• Contraction: the apostrophe stands for missing letters. It's = it is. Who's = who is. They're = they are. You're = you are.
• Possessive pronouns never take one: its, whose, theirs, yours, hers, ours.
• Plain plurals never take one either: bagels, not bagel's.

That and which

On the ACT, an essential clause uses that and takes no commas; a non-essential clause uses which and takes a comma on each end. The reliable half of that rule is the punctuation: a that-clause is never fenced off with commas, and a proper noun or a one-of-a-kind thing (Route 9, the town hall) cannot be narrowed down by an essential clause, so it takes which with its pair of commas.