Correct Use of Commas
To separate the terms of a series:
red, white, and blue
To enclose parenthetic expressions:
The report, now compiled once a year, will soon be available every month.
Before a conjunction that introduces an independent clause:
Most of the new system is installed, but the printer isn’t connected yet.
In a string of adjectives to call attention to each:
They replaced the old, noisy, slow printer.
To set off modifiers that apply to a sentence:
However, the web page isn’t finished.
After a long introductory phrase before the subject of the sentence:
Knowing the readers aren’t technical experts, the writers don’t use jargon.
To contrast elements in a sentence:
They need to add people to the testing team, not push back the schedule or eliminate testing.
Incorrect Use of Commas
To break up long groups of words:
WRONG: You can press the ESC key, to return to the menu, and not save changes.
To set off restrictive modifiers:
WRONG: People, who live in glass houses, shouldn’t throw stones.
Between a conjunction and the words it introduces:
WRONG: We need a writer but, we can’t get the funding.
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