Meter (metre): The more or less regular rhythmic pattern of stressed and unstressed syllables in verse. Four basic types of meter exist: (1) quantitative, which is based on the amount of time it takes to pronounce a particular syllable (long or short) in a poetic line (standard in Sanskrit and classical Greek and Roman verse, but rare in English due to the strongly accented nature of English and the difficulty of determining the duration of its syllables); (2) accentual, which is based on the number of stressed syllables per line (typical of Germanic verse, Old English verse included); (3) syllabic, which is based on the total number of syllables per line (common in Japanese and Romance-language verse, but fairly uncommon in English); and (4) accentual-syllabic, in which both the total number of syllables and the number of stressed and unstressed syllables are relatively consistent from line to line (standard in English).
Meter is typically described by the dominant type of foot, the rhythmic unit of a line of verse; the number of feet per line; or a combination of these two factors. Standard English feet include the iamb (˘ ´), trochee (´ ˘), anapest (˘ ˘ ´), dactyl (´ ˘ ˘), spondee (´ ´), and pyrrhic (˘ ˘). Light verse excepted, few poems are written using only one type of foot — poets generally vary the metrical pattern to avoid sounding singsongy or like a metronome — so meter is identified based on the prevailing foot. Standard English lines range from one to eight feet per line and include monometer, dimeter, trimeter, tetrameter, pentameter, hexameter, heptameter, and octameter (though monometer and octameter are rare). Common metrical combinations in English include iambic pentameter, iambic tetrameter, and trochaic tetrameter. Additional syllables, whether stressed or unstressed, exceeding the meter of a line of verse are called extrametrical.