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.

Syllable weight in linguistics
A heavy syllable is a syllable with a branching nucleus or a branching rime. A branching nucleus generally means the syllable has a long vowel or a diphthong; this type of syllable is abbreviated CVV. A syllable with a branching rime is a closed syllable, that is, one with a coda (one or more consonants at the end of the syllable); this type of syllable is abbreviated CVC. In some languages, both CVV and CVC syllables are heavy, while a syllable with a short vowel as the nucleus and no coda (a CV syllable) is a light syllable. In other languages, only CVV syllables are heavy, while CVC and CV syllables are light. Some languages distinguish a third type, CVVC syllables (with both a branching nucleus and a coda) and/or CVCC syllables (with a coda consisting of two or more consonants) as superheavy syllables.

In moraic theory, heavy syllables are analyzed as containing two moras, light syllables one, and superheavy syllables three.

The distinction between heavy and light syllables plays an important role in the phonology of some languages, especially with regards to the assignment of stress.

Basic definitions
In Ancient Greek poetry and Latin poetry, lines followed certain metrical patterns, based on arrangements of heavy and light syllables. A heavy syllable was referred to a longum and a light as a brevis (and in the modern day, reflecting the ancient terms, a longum is often called a "long syllable" and a brevis a "short syllable," potentially creating confusion between syllable length and vowel length).

A syllable was considered heavy if it contained a long vowel or a diphthong (and was therefore "long by nature" — it would be long no matter what) or if it contained a short vowel that was followed by more than one consonant ("long by position," long by virtue of its relationship to the consonants following).

An example:
 * Arma virumque cano, Troiae qui primus ab oris
 * Italiam fato profugus Laviniaque venit
 * (Aeneid 1.1-2)

The first syllable of the first word ("arma") is heavy ("long by position"), because it contains a short vowel (the A) followed by more than one consonant (R and then M) — and if not for the consonants coming after it, it would be light. The second syllable is light, because it contains a short vowel (an A) followed immediately by only one consonant (the V). The next syllable is light for the same reason. The next syllable, the second syllable of the word "virumque," is heavy ("long by position"), because it contains a short vowel followed by more than one consonant (the M and then the Q).

But, for example, the first syllable of the word "Troiae" is heavy ("long by nature") because it contains a diphthong, regardless of the sounds coming after it. Likewise, the first syllable of the second line (the first of the word "Italiam") is heavy ("long by nature") because it contains a long vowel, and it will be heavy no matter what sounds come after.

Terming a syllable "long by position" is equivalent to noting that the syllable ends with a consonant (a closed syllable), because Latin and Greek speakers in the classical era only pronounced a consonant as part of a preceding syllable when it was followed by other consonants, due to the rules of Greek and Latin syllabification. In a consonant cluster, one consonant ends the preceding syllable and the rest start the following syllable. For example, Latin syllabifies volat as vo-lat but dignus as dig-nus and monstrum as mon-strum.

Exceptions and additions
A few exceptions to and elaborations of the above rules of heavy and light syllables: As noted above, the number and order of heavy and light syllables in a line of poetry (together with word breaks) articulated the meter of the line, such as the most famous classical meter, the epic dactylic hexameter.
 * The Greek letters (zeta, xi, and psi) and their Roman equivalents Z and X (and PS) were pronounced as two consonants, so they lengthen by position despite being represented by a single character. For example, the first syllable of gaza is heavy, despite the short vowel followed only by one written consonant, because the Z was pronounced as two consonants and lengthens the syllable by position.
 * The combination plosive-liquid (usually) or plosive-nasal (sometimes) cohered in both Latin and Greek; that is, the two consonants were pronounced together with the speed of one consonant. As a result, they did not lengthen by position if the poet did not want them to (although they could if the poet chose). For example, the first syllable of patris is generally light, even though it has a short vowel followed by two consonants, because the consonants cohere (and the word is syllabified pa-tris). However, the combination aspirate-nasal or voiced consonant-nasal did not cohere and always lengthened by position.
 * In Homer and his imitators, the digamma, a sound defunct in the standard Ionic alphabet and lost from pronunciation by the classical period, was still felt enough to lengthen by position, even though it is normally not written in the Homeric poems. For example, in the line (Odyssey, 9.3), the first syllable of  is long, even though it has a short vowel followed by only one consonant, because the word was originally, and the digamma was still felt enough to lengthen the syllable by position. Since the digamma was being lost during the time when the Homeric poems were composed, recited, and written down, its effects are sometimes not felt, so that words that would have contained a digamma sometimes do not show its effects.