Cæsura is a technical term in prosody, given to an audible pause that breaks up a long line of verse.

The cæsura is an important part of Greek and Latin versification, where it plays an important role especially in the heroic verse form of the dactylic hexameter. Vergil's opening line of the Æneid:

Arma virumque cano, || Troiæ qui primus ab oris

("I sing of arms and the man, who first from the shores of Troy. . .")

displays an obvious cæsura in the middle of the line, its usual position. The cæsura can move around freely in the lines of dactylic hexameter. Technically, in dactylic hexameter, a cæsura occurs anytime when the ending of a word coincides with the ending of a metrical foot; it is usually only called one when the ending also coincides with an audible pause in speaking the line. The ancient elegiac couplet form of the Greeks and Romans contained a line of dactylic hexameter followed by a line of pentameter; the pentameter often displayed an even more obvious cæsura:

Cynthia prima fuit; || Cynthia finis erit.

("Cynthia was the first; Cynthia will be the last" -- Horace)

But the cæsura was even more important to Old English verse than it was to Latin or Greek poetry. In Latin or Greek poetry, the cæsura could be suppressed for effect in any line at will. In the alliterative verse that is shared by most of the oldest Germanic languages, the cæsura is an ever-present and necessary part of the verse form itself. Consider the opening line of Beowulf:

Hwæt! we Gar-Dena || on geardagum

("Lo! we Spear-Danes, in days of yore. . .")

and compare this to some lines from William Langland's Piers Plowman:

I loked on my left half || as þe lady me taughte
And was war of a womman || worþeli ycloþed.

("I looked on my left side, as the lady told me to, and perceived an expensively dressed woman.")

A masculine cæsura is one that occurs after a stressed syllable; a feminine cæsura follows an unstressed syllable.

Cæsuras can occur in later forms of verse; in these, though, they are usually optional. The so-called ballad metre, or the common metre of the hymnodists, us usually thought of as a line of iambic tetrameter followed by a line of trimeter, but it can also be considered a line of heptameter with a fixed cæsura at the fourth foot. Considering the break as a cæsura in these verse forms, rather than a beginning of a new line, explains how sometimes multiple cæsuras can be found in this verse form:

From the hag and hungry goblin || that into rags would rend ye,
And the spirits that stand || by the naked man || in the Book of Moons, defend ye!

In later and freer verse forms, the cæsura is optional. It can, however, be used for rhetorical effect, as in Alexander Pope's line:

To err is human; || to forgive, divine.

See also: Meter in poetry; Old English poetry; Saturnian