Pun

A pun (also known as paronomasia) is a play on words that transposes the meanings of words with similar sounds. This is usually for humorous effect, although one well known pun of serious intent is found in the Bible: Matthew 16.18:

"Thou art Peter [Greek Πετρος, Petros], and upon this rock [Greek πετρα, petra] I will build my church."

The word itself is thought to be originally a contraction of the (now archaic) pundigrion. This latter term is thought to have originated from punctillious, which itself derived from the Italian puntiglio (meaning "a fine point"). These etymological sources are reported in the Oxford English Dictionary, which nonetheless labels them "conjecture".

Although there are several varieties of puns, there are two main linguistic methods for creating them:

Homographic, where the pun exploits a word with multiple meanings. For example: "Being in politics is just like playing golf - you are trapped in one bad lie after another."
Homophonic where the pun exploits two words with similar sounds. For example: "A chicken crossing the road is pure poultry [poetry] in motion."

The compound pun is one in which multiple puns are colocated for additional and amplified effect. An example of this is the following story:

A woman had three sons who emigrated from Ireland to the USA. They prospered and soon became the owners of a large cattle ranch. They weren't, however, sure what to call it, so they wrote back to their mother for advice. She sent a one-word reply on a postcard: Focus. Puzzled, they wrote back for an explanation. Her response was: "It's where the sons raise meat". [sun's rays meet] (As a trivial aside, this pun seems to have inspired a number of real Focus Ranches, for example: http://www.coloradoduderanches.com/focus-ranch/. )

Sometimes puns can be used in a name. For instace the name "Justin Tyme" sounds like "just in time." This sort of naming is found in many works of fiction, for example The Eyre Affair, the Carmen Sandiego computer games.

Puns are also found in serious literature. See Alexander Pope, James Joyce, Vladimir Nabokov, and others discussed under word play.

Numerous pun formats exist, see also:

Quotations

"He that would pun, would pick a pocket." Alexander Pope, punster
"Blunt and I made atrocious puns. I believe, indeed, that Miss Blunt herself made a little punkin, as I called it." Henry James
"Pun: (n) the lowest form of humour" Samuel Johnson
"But the height of wit." Common rebuttal to the above