I write everyday at work. I edit other people’s writing often. And I read a lot as well.
The most common grammatical error I see — made even by professional writers — is the use of a comma before “and” when combining two thoughts.
People often don’t use the comma when its critically needed…or they stick it in when it’s unnecessary.
Here’s the scoop:
A. When you are joining two separate stand-alone thoughts (complete sentences), you need the comma.
Example: I love correct grammar, and I shout for joy when it is right!
Quick test to make sure you’ve got it right: chop the sentence in half at the “and.” If the clauses stand alone (meaning they have a subject, verb, and predicate), then the sentence needs a comma.
B. When you are joining two fragments, you don’t need the comma.
Example: I love correct grammar and hate sloppy stream-of-consciousness writing.
Quick test: When you chop the sentences apart at the “and,” you can see that the second phrase can’t stand alone–it doesn’t have a subject!
This is an easy thing to remember…I hope you’ll help keep me sane by following this easy grammar rule.