They were adopted to describe the equivalent meters in English accentual-syllabic verse.

Accentual-syllabic verse is highly regular and therefore easily scannable.

As in accentual-syllabic verse, there is some flexibility in how one counts syllables.

In accentual-syllabic verse we could describe a bacchius as a foot that goes like this:

This is a form of accentual verse, as opposed to our accentual-syllabic verse.

In accentual-syllabic verse an iamb is a foot that has the rhythmic pattern:

In English accentual-syllabic verse, iambic trimeter is a line comprising three iambs.

Accentual-syllabic verse is an extension of accentual verse that also fixes the syllables.

In accentual-syllabic verse an antibacchius consists of two accented syllables followed by one unaccented syllable.

The term was adopted to describe the equivalent meter in accentual-syllabic verse, as composed in English, German, Russian, and other languages.

Accentual-syllabic verse is an extension of accentual verse which fixes both the number of stresses and syllables within a line or stanza.

In the accentual-syllabic verse of English, German, and other languages, iambic trimeter is a meter consisting of three iambs (disyllabic units with rising stress) per line.

In the early 20th Century, accentual-syllabic verse was largely supplanted by free verse through the efforts of Modernists such as Ezra Pound and Amy Lowell.

While individual lines may have a regular syllabic structure, this is not kept constant over the poem - only the stress pattern is consistent - as otherwise the poem becomes accentual-syllabic verse.

This terminology was adopted in the description of accentual-syllabic verse in English, where it refers to a foot comprising an unstressed syllable followed by a stressed syllable (as in a-bove).

In accentual-syllabic verse, it is a line of iambic hexameter - a line of six feet or measures ("iambs"), each of which has two syllables with an unstressed syllable followed by a stressed syllable.

The foot is the basic metrical unit that generates a line of verse in most Western traditions of poetry, including English accentual-syllabic verse and the quantitative meter of classical ancient Greek and Latin poetry.

Though it has not regained its position of dominance within English poetry, accentual-syllabic verse remains viable and popular in the 21st century, as evidenced by the success of such poets as Richard Wilbur and the various New Formalists.

In quantitative meter (such as the meter of classical verse), it consists of three short syllables; in accentual-syllabic verse (such as formal English verse), the tribrach consists of three unstressed syllables.

It is common in languages that are syllable-timed, such as Japanese or modern French or Finnish - as opposed to stress-timed languages such as English, in which accentual verse and accentual-syllabic verse are more common.

Accentual verse continued in common use in all forms of Middle English poetry until the codification of accentual-syllabic verse in Elizabethan poetry, whereupon it largely disappeared from literary poetry for three hundred years, but remained very popular in folk poetry.