One thing is spoken of as if it were another. A metaphor asserts an identity or close resemblance without using “like” or “as.” “Time is a thief,” “the classroom was a zoo,” “her voice was velvet.” The comparison is implicit and compressed, inviting the reader to transfer qualities from the vehicle to the tenor.

Metaphors shape thought as well as style. They can make abstract ideas concrete, reveal hidden similarities, and generate new ways of seeing. Dead metaphors—“the foot of the mountain,” “the head of the table”—have become so familiar that their figurative origin is almost invisible. Live metaphors still surprise and illuminate.

Poets and orators rely heavily on metaphor, but everyday speech is full of it as well. Scientific and philosophical language also uses metaphor, sometimes consciously, sometimes not. The risk is that an unnoticed metaphor can constrain understanding. The reward is the sudden clarity or emotional force that a well-chosen metaphor provides. Learning to recognize and craft metaphors is part of becoming a more precise and imaginative user of language.