The Comma Map — Which Comma Problem?

You're halfway through a sentence — an email, a bit of homework, a message that suddenly feels like it matters — and your finger hovers over the comma key. You know one belongs somewhere. You're just not sure which job it's meant to be doing.

Here's the thing. The comma does more jobs than any other mark in English, which is exactly why it feels slippery. But it isn't one rule with a dozen exceptions. It's really four jobs. Once you can name the job in front of you, you know which page to open — and you can stop trying to swallow the whole system in one sitting.

This page teaches nothing. It only points. Find the job that matches what you're writing, click through, and sort that one sentence.

Which comma problem do you have?

1. You're listing things. Three or more items in a row, and you need commas to keep them from running into each other — including the vexed question of the comma before and (the Oxford comma [US: serial comma]). "We packed sandwiches, fruit, crisps and juice." → Commas in Lists & the Oxford Comma (2.1)

2. You're joining two full clauses — or you've joined them badly. Two parts that could each stand as their own sentence, stitched together with a coordinating conjunction (the FANBOYS: for, and, nor, but, or, yet, so). This is also where you fix a comma splice. "I wanted to go out, but it started raining." → The Comma Before a Coordinating Conjunction & Comma Splices (2.2) (If the join itself feels broken — a run-on, or you're unsure what counts as a clause — that's structure, not punctuation. See Pillar 3: Clause Types & Run-ons and Pillar 2: Conjunctions.)

3. Your sentence opens with a scene-setter. A word, phrase or clause sits at the front before the main idea gets going, and you're unsure whether a comma should follow it. "After the meeting, we went to the pub." → The Comma After an Introductory Element (2.3)

4. You're dropping in extra, non-essential information. A name, a detail, an aside you could lift out without breaking the core meaning — set off with commas at both ends. "My brother, who lives in Bristol, is visiting next week." → Commas Around Non-restrictive Elements (2.4) (Whether that information is genuinely "extra" or actually essential is a structure question — restrictive vs non-restrictive lives in Pillar 3. The commas only land once you know.)

Commas mostly mark structure; they don't create it. So if none of the four quite fit — the sentence feels broken, or you're really wrestling with clauses and conjunctions rather than punctuation — head back up to the Pillar 6: Punctuation hub and take the structural route through Pillars 2 and 3 first.

Pick the one job in front of you. Sort that sentence. Leave the rest for later — nobody's born knowing this.