Accentual-syllabic verse is an extension of accentual verse which fixes both the number of stresses and syllables within a line or stanza. Accentual-syllabic verse is highly regular and therefore easily scannable. Usually, either one metrical foot, or a specific pattern of metrical feet, is used throughout the entire poem; thus one can speak about a poem being in, for example, iambic pentameter. Poets naturally vary the rhythm of their lines, using devices such as inversion, elision, masculine and feminine endings, the caesura, using secondary stress, the addition of extra-metrical syllables, or the omission of syllables, the substitution of one foot for another.
Accentual-syllabic verse dominated literary poetry in English from Chaucer's day until the 19th century, when the freer approach to meter championed by poets such as Samuel Taylor Coleridge and Ralph Waldo Emerson and the radically experimental verse of Gerard Manley Hopkins and Walt Whitman began to challenge its dominance. In the early 20th century, accentual-syllabic verse was largely supplanted by free verse in literary poetry through the efforts of Modernists such as Ezra Pound and Amy Lowell. Nonetheless, some poets, such as Robert Frost, W. H. Auden, Keith Douglas, Robert Lowell, Philip Larkin, Howard Nemerov, James Merrill, Derek Walcott, Geoffrey Hill, Seamus Heaney and Derek Mahon continued to work (though not exclusively) in accentual-syllabic meters throughout the century.
