Punctuation
Commas
A comma is a pause that prevents misreading — not decoration after every word.
Why this happens
Commas mark pauses and logical boundaries, but writers often omit them before coordinating conjunctions joining independent clauses, or add them where no pause belongs. Lists, introductory elements, and nonessential clauses each follow predictable patterns — errors usually come from rushing or mirroring speech without checking sentence structure.
See it in a sentence
IncorrectShe finished the draft and she sent it to her tutor.
CorrectShe finished the draft, and she sent it to her tutor.
Teaching note: Two independent clauses joined by and need a comma before the conjunction.
IncorrectAfter the meeting we revised the introduction.
CorrectAfter the meeting, we revised the introduction.
Teaching note: Introductory phrase after the meeting needs a comma before the main clause.
IncorrectThe report which was overdue is finally complete.
CorrectThe report, which was overdue, is finally complete.
Teaching note: Nonessential which clause adds extra detail — set it off with commas on both sides.
More examples
We invited Maya, James, and Priya to the workshop.
Oxford comma before and in a list of three or more items prevents ambiguity.
On Tuesday, however, the deadline moved again.
Introductory day phrase and however as interrupter both need comma boundaries.
The CEO, who joined last year, approved the budget.
Who joined last year is extra information — commas show it could be removed without changing core meaning.
She said she would call, but she never did.
Comma only when both sides could stand alone as sentences; do not comma-join fragments incorrectly.
Quick check
Before the exam students reviewed their notes in the library.
Show the fix
Before the exam, students reviewed their notes in the library. Add a comma after the introductory phrase Before the exam.
Practice this topic in Wrytesmart
Open the grammar workspace to complete interactive exercises for commas. You will spot errors, fill blanks, and transform sentences — always with teaching notes that explain the principle, not just the correction.
Master commas in context
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