A catalectic line is a metrically incomplete line of verse, lacking a syllable at the end or ending with an incomplete foot. One form of catalexis is headlessness, where the unstressed syllable is dropped from the beginning of the line.

A line missing two syllables is called brachycatalectic. A line with an additional syllable is called hypercatalectic.

Poems can be written entirely in catalectic lines, or entirely in acatalectic (complete) lines, or a mixture, as in the following carol, composed by Cecil Frances Alexander in 1848. The 7-syllable lines are catalectic:

It has been argued that across a number of Indo-European languages, when the two types of line are mixed in this way, the shorter line tends to be used as a coda at the end of a period or stanza.

It has been argued that catalexis can be divided into two types. (Here "x" stands for an anceps syllable.)

An example of a blunt line becoming pendant in catalexis is Goethe's poem Heidenröslein, or, in the same metre, the English carol Good King Wenceslas:

Another example is the children's song Here We Go Round the Mulberry Bush, of which the first stanza ends as follows:

In all of these songs, when they are set to music, there is a lengthening of the penultimate syllable in order to equalise the two lines. However, there is not enough evidence to tell if a similar phenomenon occurred in Ancient Greek.