1)Irony is a stylistic device in which the contextual meaning of a word is directly opposite to its dictionary meaning. Irony occurs when a person says one thing but really means something else.
Example: Never argue with a fool. People might not know the difference.
2)Zeugma is a stylistic device that plays upon two different meanings of the word. The effect comes from the use of a word in the same formal (grammatical) relations, but in different semantic relations with the surrounding words in the phrase or sentence, due to the simultaneous realization (in one text) of the literal and figurative meaning of a word.
Example: A leopard changes his spots, as often as he goes from one spot to another.
3)Pun is another stylistic device based on the interaction of two meanings of a word or phrase. For example, thus the title of one of Oscar Wilde's plays, "The Importance of Being Earnest" has a pun in it, inasmuch as the name of the hero and the adjective meaning 'seriously-minded' are both present in our mind.