Iambic trimeter

iambic trimeter is a meter of poetry consisting of three iambic units per line.

In ancient Greek poetry, iambic trimeter is a quantitative meter, in which a line consisted of three iambic metra and each metron consisted of two iambi. In the dramatic forms of tragedy and comedy, It was used mainly for the verses "spoken" by a character, that is, the dialogue rather than the choral passages.

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.

Basic form
The iambic trimeter derives its name from its essential shape, which is three metrical units (hence "trimeter") which are each basically iambic in form. The iambic metron has the following shape (where the "x" is an anceps, the "-" is a longum, and the "u" is a brevis):


 * x - u -

The long-short-long structure is known as a cretic, so the basic metrical unit of the iambic trimeter may be said to be the following: anceps-cretic. The trimeter simply repeats this structure three times, with the resulting shape as follows:


 * x - u - x - u - x - u -

Note that, as always, the final syllable can observe the phenomenon of brevis in longo, so it may actually be short or long.

A straightforward example of the structure:


 * u - u - - - u - - - u -
 * (Euripides, Hippolytus 1053)
 * (Euripides, Hippolytus 1053)

Caesura and Bridge
A caesura is usually found after the fifth or seventh element of the line, or, in other words, after the second anceps or the brevis of the second cretic. In the example above, it is found after the fifth element, as so (with || representing the caesura):


 * u - u - - || - u - u - u -

Finally, Porson's Law is observed, which means here that if the first or third anceps is long, there cannot be a word-break after that anceps. The second anceps is free from this constraint, because a word-break at that point would be a main caesura.

Resolution and Substitution
The trimeter also observes the phenomena of resolution and substitution, allowing a greater variety of possibilities. In tragedy, resolution is fairly uncommon, and substitution occurs almost exclusively to accommodate personal names that otherwise could not fit the meter. In comedy, which is closer to casual speech, resolution and substitution are fairly common.

In both tragedy and comedy, though, the third metron is usually left alone; resolution and substitution in the final metron of the line is rare. Also, in tragedy, resolution and substitution are virtually never consecutive, and two instances of either in the same line is extremely rare. Finally, as usual, when resolution or substitution occurs, the two shorts standing in place of a long, an anceps, or one short are almost always within the same word-unit.

Accentual-syllabic iambic trimeter
In English similar accentual-syllabic metrical systems, a line of iambic trimeter consists of three iambic feet. The resulting six-syllable line is very short, and few poems are written entirely in this meter.

The 1948 poem "My Papa's Waltz" by Theodore Roethke uses the trimeter:
 * ...We romped until the pans
 * Slid from the kitchen shelf;
 * My mother's countenance
 * Could not unfrown itself.

William Blake's "Song ('I Love the Jocund Dance')" (1783) uses a loose iambic trimeter that sometimes incorporates additional weak syllables:
 * I love the jocund dance,
 * The softly breathing song,
 * Where innocent eyes do glance,
 * And where lisps the maiden's tongue.


 * I love the laughing gale,
 * I love the echoing hill,
 * Where mirth does never fail,
 * And the jolly swain laughs his fill.

As a component of common meter
The English iambic trimeter is much more frequently encountered as one-half of the common meter, which consists of alternating iambic tetrameter and trimeter lines:
 * To Mercy, Pity, Peace, and Love,
 * All pray in their distress:
 * And to these virtues of delight
 * Return their thankfulness.
 * William Blake, "The Divine Image," Songs of Innocence, 1789