01 The Only Four Jobs a Comma May Do
If it isn’t one of these four, delete it
1 · After an introductory element: After the storm, we left. 2 · Around non-essential information (a pair):
My sister, a chemist, agreed. 3 · Between items in a series: red, white, and blue. 4 · Before a FANBOYS joining two ICs: It rained, so we left.02 Essential vs. Non-Essential
The remove-and-test
Information that can be removed without changing
which thing you mean is
non-essential — wrap it in a pair of commas. Information that identifies which one is
essential — no commas.
The runner , who finished first , set a record only if there’s one runner; if it tells you
which runner, drop both commas.
03 The Pause Comma (Most-Tested Trap)
Never comma between a subject and its verb
You would
pause after a long subject, but you may not
comma there:
× The scientists who led the study, published their results. A comma is not a breath mark. If it isn’t doing one of the four jobs, it’s wrong.
Ready to practice?
14 questions for this session — 4 guided (label the structure first), 6 on the clock, and 4 in home practice. Every timed score feeds your sub-skill Error Log.
Open Session 04 Exercises →