Free verse (or vers libre) is a style of poetry which is based on cadences that are more irregular than those of traditional poetic meter. While the basic rhythmic unit of most traditional poetic forms is the foot, free verse tends to use longer units, such as the line or stanza.
Free verse may or may not use rhyme. When it is used, it tends to follow a looser pattern than would be expected in formal verse.
The practice of poets who write in free verse was well described by Ezra Pound, who wrote: "As regarding rhythm: to compose in the sequence of the musical phrase, not in sequence of a metronome." Pound's friend T. S. Eliot wrote: "No verse is free for the man who wants to do a good job."
As the name vers libre suggests, this technique of using more irregular cadences is often said to derive from the practices of 19th century French poets like Stéphane Mallarmé. However, in English it can be traced back at least as far as the King James Bible.
Many formalist poets find free verse to be aesthetically useless, or, at the least, less capable of expression. One such poet, Robert Frost, said that writing free verse was like "playing tennis without a net".