Commas

Comma Clara

“Pause here? Pause there? Who's counting?”

What's the problem?

Commas show how a sentence is built, not where you would pause. In this course: commas mark the end of introductory clauses; under our house style, a comma separates two independent clauses joined by a coordinating conjunction (and, but, or, so, yet); and paired commas enclose information presented as supplementary rather than identifying which person or thing is meant. Commas also separate list items (house style uses the serial comma), separate adjectives that each describe a noun independently, and set off the name of someone being addressed. There is legitimate variation: short introductory phrases and some short compound clauses often go without a comma in other styles. And "could I remove it?" isn't a sufficient test for extra information: removing an identifying clause can leave a grammatical sentence with a different meaning.

Context: The team's project lead is already identified as Rosa. The writer is mentioning her name as supplementary information, and is listing three groups.

✗ Comma trouble: When the audit ended the project lead Rosa thanked the team members, the auditors and the IT staff.
✓ Clear structure: When the audit ended, the project lead, Rosa, thanked the team members, the auditors, and the IT staff.
Why it works: The comma after "ended" marks the end of the introductory clause. Paired commas present "Rosa" as supplementary, since the role already identifies who is meant. The comma before "and" follows our serial-comma house style; many styles omit it, and that's also standard when the meaning stays clear.