A Simile is a figure of speech in which things that are in most respects unlike are said to be alike. The comparison is made definitely by the use of like, or as, or so; thus:

"Like a merry guest's farewell, the day in brightness passed."

"How far that little candle throws its beams; So shines a good deed in a naughty world."

You must not think that a simile is used whenever two things are said to be alike. When a person says that one apple is like another, he has used plain, or literal, language, for the two apples are in most respects alike.