In Greek and Latin meter

Meter (poetry)

In poetry, metre is the basic rhythmic structure of a verse or lines in verse. Many traditional verse forms prescribe a specific verse metre, or a certain set of metres alternating in a particular order. The study of metres and forms of versification is known as prosody...

, a short syllable

Syllable weight

In linguistics, syllable weight is the concept that syllables pattern together according to the number and/or duration of segments in the rime. In classical poetry, both Greek and Latin, distinctions of syllable weight were fundamental to the meter of the line....

 at the end of a line can be counted as long; this phenomenon is known as brevis in longo.

The term comes from Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

, and means "a short [syllable] in place of a long [syllable]." Brevis in longo is possible in any classical meter that requires a long syllable at the end of a line, including dactylic hexameter

Dactylic hexameter

Dactylic hexameter is a form of meter in poetry or a rhythmic scheme. It is traditionally associated with the quantitative meter of classical epic poetry in both Greek and Latin, and was consequently considered to be the Grand Style of classical poetry...

 and iambic trimeter

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...

.

Brevis in longo is quite distinct from the metrical element anceps

Anceps

In Greek and Latin meter, an anceps syllable is a syllable in a metrical line which can be either short or long. An anceps syllable may be called "free" or "irrational" depending on the type of meter being discussed....

, which is a syllable that can be either short or long. These two phenomena are often confused, but there are differences between the two. For example, an anceps will be considered short or long in accordance with its natural length. A brevis in longo, on the other hand, will always be considered long, even though its natural quantity is short: the pause at the end of the line adds weight enough for even a short syllable to be counted as long.

An additional distinction is the following: some classical meters have an anceps syllable in certain positions in the line (at the beginning of each metron, for example, in iambic trimeter). The placement of the anceps is dictated by the type of meter. However, all classical meters have the possibility of a brevis in longo, proving that the brevis in longo is a different phenomenon.