Wikipedia has a wonderful explaination of the history and usage of puns.
Walter Redfern (in Puns, Blackwell, London, 1984) succinctly said: “To pun is to treat homonyms as synonyms“.
They explain the different varieties of puns. (Homographic , Heteronymic, Homophonic and Double-sound.
“The pun is mightier than the sword.” – James Joyce
“The eleventh pun always gets a laugh, even if no pun in ten did.”
Whatya think?