A Comma Conundrum

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WHEN TO USE A COMMA BETWEEN INDEPENDENT CLAUSES.

A reader posted the following question: When can you use a comma to separate two independent clauses?

The answer: First, we at Syntaxis are impressed by your use of grammar terminology. An independent clause, for those who are unfamiliar with the term, is a group of words containing a subject and a verb, and capable of standing alone as a sentence.

Here are two independent clauses:

the oil company executives were questioned extensively
their explanations were unsatisfactory

You could combine the clauses like this:

The oil company executives were questioned extensively, but their explanations were unsatisfactory.

But not like this:

The oil company executives were questioned extensively, their explanations were unsatisfactory.

The above sentence, with just a comma between the two clauses, is called a comma splice. That is not a good thing; it is considered an error. Think of the comma as being too dainty and delicate to hold apart two independent clauses without the assistance of a coordinating conjunction.

Some good news is that there are only seven such conjunctions, and you can use the mnemonic device (memory aid) fanboys to help you remember them.

for
and
nor
but
or
yet
so

A very common punctuation pattern is:

[independent clause][comma][coordinating conjunction][independent clause].

Here are two additional examples of that pattern:

Mark sent the report, and Jane called the client.
She needed some extra money, so she worked a lot of overtime.

Cautionary note: Do not use a comma before the however in the following example.

The oil company executives were questioned extensively; however, their explanations were unsatisfactory.

Note the semicolon. A comma in this position would be incorrect; it would once again create a comma splice, because you are essentially beginning what could be a new sentence. One alternative to the semicolon in this case would be a period:

The oil company executives were questioned extensively. However, their explanations were unsatisfactory.