pentameter

pentameter, in poetry, a line of verse containing five metrical feet. In English verse, in which pentameter has been the predominant metre since the 16th century, the preferred foot is the iamb—i.e., an unstressed syllable followed by a stressed one, represented in scansion as ˘ ´.

Geoffrey Chaucer employed iambic pentameter in The Canterbury Tales as early as the 14th century, although without the regularity that is found later in the heroic couplets of John Dryden and Alexander Pope. Most English sonnets have been written in iambic pentameter, as in this example from Shakespeare:

Shakespeare also used pentameter in his blank-verse tragedies.