Pun

Pun – A play on words.  The following limerick plays with two different meanings of the word “fly”, the homonyms (same-sounding but different-meaning words) “flea” and “flee”, and the homonyms “flew” and “flue” (an air or smoke passage). 

A flea and a fly in a flue
Were imprisoned, so what could they do?
Said the fly, “Let us flee.”
Said the flea, “Let us fly.”
So they flew through a flaw in the flue.