What's the difference between a simile, a metaphor, and an analogy?

While these three terms are related, their meanings are subtly different.

An analogy is a comparison, usually of two things that don't seem to have anything in common.

At the most basic level, an analogy is a form of speech that shows similarity between things that might seem different at first. But an analogy isn't just a form of speech. It can also be a logical argument. (If two things are alike in some ways, they are alike in some other ways as well.)

Analogy is often used to help provide insight by comparing an unknown subject to one that is more familiar. It can also show a relationship between pairs of things. This form of analogy is often used on standardized tests in the form "A is to B as C is to D."

The dictionary defines a metaphor as a figure of speech that uses one thing to be another when making a comparison between the two. For example, "All the world is a stage," is a metaphor comparing the whole world to a theater stage. Metaphors can be very simple, and they can function as most any part of speech. "The spy shadowed the woman" is a verb metaphor. The spy doesn't literally cast his shadow on the woman, but he follows her so closely and quietly that he resembles her own shadow.

A simile is also a form of an analogy that compares two different things. But a simile always uses the word "like" or "as" within the phrase and is more explicit than a metaphor. For example, "All the world is like a stage." Another simile would be: "The spy was close as a shadow." Both metaphors and similes can be used to enhance writing.