Dactylic hexameter
Dactylic hexameter is a line of six feet, mostly dactyls, the meter of the ancient Greek and Latin epics.
Longfellow tried the old epic line in English, with the stressed syllables in capitals.
THIS is the FORest priMEval. The MURmuring PINES and the HEMlocks
Henry Wadsworth Longfellow, "Evangeline", 1847
What it is
Each line has six feet. The first four can be dactyls or spondees, the fifth is nearly always a dactyl and the sixth is a spondee or a short foot. It was the line of the Iliad, the Odyssey and the Aeneid, so it carries the weight of the epic.
Why it matters to a writer or editor
When an English poet writes in dactylic hexameter, the aim is a feeling of grand, rolling scale. If you are editing one, read it aloud and make sure the line pauses are where the sense pauses.
Frequently asked questions
Why is dactylic hexameter hard in English?
Greek and Latin build lines from long and short syllables, while English builds them from stressed and unstressed ones, and English has fewer natural dactyls. The result is usually a looser, more galloping line.