A pun is a form of wordplay that exploits multiple meanings of words for an amusing or rhetorical effect — it’s the literary equivalent of a double entendre. The word’s etymology comes from the Latin, meaning “to pound,” which refers to the process by which meat was made into sausage: meat was pounded into small pieces with a mallet before being cooked in water and spices.
Puns are often considered humorous, but they can also be used as serious forms of poetry and rhetoric. In most cases, puns rely on multiple meanings of words, or different interpretations of the same meaning. They are often used in conversation and in informal writing, but they appear in literature too.
Puns may be regarded as wit, and they are sometimes used to intentionally provoke laughter. In modern English, we call those kinds of jokes “gag” — for example: “That’s my favorite gag about the guy who got hit by lightning.”
Puns can also be used to create serious or thought-provoking effects. For example, in William Shakespeare’s “Much Ado About Nothing,” Benedick makes his famous line, “I would not wish any companion in the world but my friend” (Act III, Scene 1). This line is funny because he says it with such seriousness and intensity that it seems absurd for him to say such a thing about his friend Claudio who has just jilted Hero (the woman Benedick loves).