Which type of expression differs from the literal meaning of its words?

The type of expression that differs from the literal meaning of its words is an idiom. Idioms are phrases or expressions whose meanings are not predictable from the individual words within them. For instance, when someone says “it’s raining cats and dogs,” they do not mean that actual cats and dogs are falling from the sky; rather, they are conveying that it is raining very heavily. This disconnect between the literal and intended meanings is what characterizes idioms.

In contrast, a simile makes a direct comparison between two things using the words "like" or "as," which while figurative, is based on the meanings of the words involved. A metaphor also involves comparison but does so more directly by stating that one thing is another, which still carries an implied meaning rather than veering away from the literal entirely. Hyperbole is an exaggerated statement that is not meant to be taken literally but focuses more on emphasis rather than a complete departure from the literal meaning. Each of these other options employs figurative language but does not share the same level of non-literal deviation as idioms.