In poetry, a tetrameter is a line of four metrical feet: Poetry (ancient Greek: poieo = create) is an art form in which human language is used for its aesthetic qualities in addition to, or instead of, its notional and semantic content. ... In verse, a foot is the basic unit of meter used to describe rhythm. ...
And the sheen of their spears was like stars on the sea (Anapaest tetrameter) (Byron, "The Destruction of Sennacherib")
"You who are bent and bald and blind" (Iambic tetrameter, except for the first foot which is a trochee) (W.B. Yeats, "The Wanderings of Oisin") A trochee is a metrical foot used in formal poetry. ... A 1907 engraving of Yeats. ...
The use of a tetrameter line with a silent final beat is especially common in the second and fourth lines of a four-line tetrameter stanza, so that the eighth and sixteenth beats of the stanza as a whole are silent.
Just as the four beats of tetrameter may be conceived as two times two, the six beats of pentameter may be conceived as three beats, each of which is subdivided into two beats, with offbeat syllables between the beats, and the final beat silent.
Tetrameter is the underdog to pentameter (and, for about the last 100 years, free verse) but its charms are worth exploring.
An extra or missing syllable may be tolerated, and an occasional reversal of the ta TUM pattern (to TA tum) is common, even desirable as a way to avoid monotony.
Like any other meter, tetrameter can be rhymed or unrhymed.
A very common verse form, ballad verse, features alternate lines of iambic tetrameter and trimeter (three feet, six syllables), typically in rhymed, four-line stanzas.