while

A conjunction:

            while the dog slept ...

Avoid using while to mean though or whereas when there is a danger of ambiguity:

            Incorrect:    While most Canadians speak English, the Quebecois speak French

            Write:             Though most Canadians ...

Do not confuse the adverb awhile with the noun phrase a while:

            awhile: adverb—We stood awhile on the dock; awhile back.

             a while: article and noun—We stood for a while on the dock; a while ago; wait a while.

Note: not whilst