Punctuating Relational Words
The purpose of this lesson and all those before it is to make certain that you never again write, "Although she could not be certain of her future'' with a period at the end as if it were a sentence--and that you never again write, "There is convenient parking at the theater, however, there is a fee.'' The "although'' clause is not a sentence, and the "however" run-on is two sentences.

Words that relate one idea to another do not always join one sentence to another. Those that do join sentences always stand at the beginning of the words they introduce, even if those words happen to come before what they are joined to, as in the following sentences, where the unit to be joined is underlined and the joiner is in bold type:

John's knees grow weak whenever Ruby smiles.
Whenever Ruby smiles John's knees grow weak.

Words that relate ideas without joining structures never come in the first of the two sentences, but they can move about within the second of the two sentences they relate. Being transitional, they normally appear close to the beginning of the second sentence although (for variety) they are often moved to the right. Examples:

There is plenty of convenient parking at the theater. However, there is a fee.
There is plenty of convenient parking at the theater. There is, however, a fee.
There is plenty of convenient parking at the theater. There is a fee, however.

This follow-up lesson gives you practice in applying these ideas to specific punctuation situations.