Recipe

Place a comma

Use when: you're deciding whether a specific spot in a sentence needs a comma, and which rule (if any) governs it

Goal: the correct comma decision at that spot, backed by a structural rule -- never a guess about where you'd pause

Taught in Commas You Must Not Use

1. 1

   Look for a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so). If one is present, run the test: could you drop a period right where the conjunction sits and get two complete sentences, one on each side?

   Example

   I called the office, and someone finally answered. Both halves pass the drop-a-period test, so the comma before and is correct. She reviewed the report and filed it. Filed it has no subject of its own -- it fails the test -- so no comma belongs before and.

   • yes, both sides pass the test — place a comma immediately before the FANBOYS word (Structure #1); the comma decision at this spot is settled.
   • no, one side has no subject and verb of its own — no comma belongs at this FANBOYS word; move to Step 2 and check the rest of the sentence for a different comma job entirely.

   Why: comma-before-FANBOYS is only correct when it marks the seam between two independent clauses; pattern-matching "comma before and" instead of running the test is the single most common comma mistake in this chapter.

2. 2

   Look at everything sitting before the sentence's main subject and verb: a single word, a phrase, or a dependent clause.

   Example

   After the long meeting, we finally ate. The opening phrase runs four words and sets up the main clause, so the comma marks where it ends. In 1999 the company launched. A short opener like this one can skip the comma.

   • the opener is a dependent clause, or a phrase of more than a few words — place a comma right after it, at the boundary where the setup ends and the main clause begins.
   • the opener is a single short prepositional phrase (a few words, like "In 1999") — the comma may be dropped without creating confusion, though writing it in every time is never wrong.

   Why: an introductory element is setup, not part of the sentence's core claim. The comma tells the reader where the setup hands off to the main clause.

3. 3

   Find the chunk you're considering: a nonrestrictive clause, an appositive, a parenthetical, or a direct address. Run the deletion test: remove it and check whether the sentence still says which thing it's about.

   Example

   Our dog, which is twelve, still chases squirrels. Delete which is twelve and our dog still refers to the same one dog -- nonessential, commas on both sides. Drivers who speed will be fined. Delete the clause and the sentence now claims something about drivers in general -- essential, no commas.

   • yes, the sentence still identifies the same thing without it (nonessential) — fence the chunk off: a comma on both sides if it sits in the middle, a single comma in front if it sits at the end.
   • no, deleting it changes which thing the sentence refers to (essential/restrictive) — no commas at all, no matter where the chunk sits.

   Why: this test separates a bonus fact, which gets fenced off, from information the sentence needs just to say which thing it's about, which never does. Getting it backward doesn't just misplace a comma -- it changes the sentence's claim.

4. 4

   Ask whether the spot follows a fixed format instead of a structural test. Two cases: three or more items in a list, or a date, address, or quotation in running text.

   • three or more items in a series — a comma between every item, including one before the final conjunction (the serial comma, this course's house style).
   • a date, address, or direct quotation — apply that convention's own fixed comma placement.

   Why: these commas don't depend on any judgment call about clauses or essential information. They're a fixed format, applied the same way every time.

5. 5

   Before settling on the comma, or the absence of one, run one more check. Compare it against the three placements that are always wrong. Never put a comma between a subject and its own verb. Never put one before a FANBOYS word joining anything smaller than two independent clauses. Never put one around a restrictive, essential element.

   Why: these three checks mirror Steps 1 and 3 -- the same tests, run backward, to catch a comma that shouldn't be there at all, rather than one that's missing.