The basic unit of poetry is called a "foot" - this was originally a measure (Greek metron) of the time it takes to raise one foot in dancing or marching and put it down again. It's similar to a bar in music, or the off-beat + the on-beat in jazz and rock. By definition, therefore , a foot has two equal parts (equal in time, that is). Lifting the foot up (which the Greeks called arsis, and thumping it down again (which they called thesis). A foot consists of arsis (one long syllable, usually) followed by thesis (another long syllable, or possibly two short ones making up the same amount of time). The foot with two longs is called a spondee, the foot with a long and two shorts is called a dactyl (from the Greek for finger - your finger has a long joint and two short ones). Sometimes found at the end of a line (see below) is a trochee
The dancing would have been accompanied by music, and the music could of course have been the human voice. The dancers keep "in time" with the music, which is divided into a number of "feet" - during each of which the dancers raise and lower a foot. But although music supplied by instruments can be continuous, a singer has to breathe! Thus the song/poem tended to be split up into equal chunks allowing the singer to take breaths at regular intervals. This is the origin of the line (which of course only became an actual line much later when a poem could be reproduced in writing). Frequently there's a missing bit of the last foot of a line (see hexameter), corresponding to the point where the breath was taken. Most lines also contained a subsidiary pause about halfway through, where the singer could take a short breath - thus a line of verse can be "cut" into two sections - the place where the cut happened was called the caesura (Latin for cutting).
The line used by Homer and the Greek epic poets was adapted by the Romans. It has 6 (Greek hex) metra, or feet, usually a mixture of dactyls and spondees. Click on the ear icon to hear the sound! The first line, about horses galloping, has an unusual preponderance of dactyls, while the second is nearly all spondees, giving a very slow and solemn effect. After listening to these, you'll appreciate why Virgil normally prefers a fluid mixture of the two types of feet. Every line, however will always end with the pattern | or | . A red horizontal line | shows where the foot ends, and // shows the caesura.
Click on the ear!
|quadruped-|||ante put|||-rem soni|||-tu // quatit|||ungula|||campum|
|at re-|||gina gra-|||vi // iam-|||dudum|||saucia|||cura|
|vulnus a-|||lit ve-|||nis // et|||caeco|||carpitur|||igni|