The Rhythm of Latin Poetry :: “Scanning” Meter

English poetry is based on a sequence of stressed and unstressed syllabus. Latin does have stressed and unstressed syllabus but Latin meters are quantitative, meaning they are formed by regular sequences of long (longum) and short (breve) syllables. A long syllable takes twice as long to pronounce as a short one. These patterns of long and short syllables create the rhythm of the Latin poetry. The process of identifying which syllables are long and which are short is called “scanning” or “scansion.”

1. The basic rule of scanning

A syllable is long if:

1. it is long by nature, i.e., it contains a long vowel or a diphthong
   1. long vowels are marked with a macron in a good dictionary (e.g., ā)
   2. diphthongs are ae, au, ei, eu, oe (and rarely ui); note that reverses, e.g., ea or eo or ie or ua are not diphthongs.
2. it is long by position, i.e., its vowel followed by
   1. two or more consonants (even if the consonants are in different words); 

e.g., ēst mēns dēdūcta (Catullus 75.1). The e in est is considered long for the purposes of scanning because it is followed by two consonants.

1. • a double consonant (x = ks; z = sd); e.g., dilēxī tum tē (Catullus 72.3)

Long syllables can be marked with a — symbol.

If a syllable is not long, then it is short (u).

2. Notable modifications to the above rules:

1. a mute consonant (p, b, t, d, c, g) followed by a liquid (l, m, n, r) does not necessarily make the preceding syllable long by position (although it can). This is because these clusters can be pronounced as a single utterance; say “cr” or “bl” and note how the first letter merges with the second.
2. h is never considered a consonant. When a word ends with a consonant and is followed by a word beginning with h, that syllable is not long by position: e.g., amăt hunc
3. remember that ‘i’ is sometimes a consonant (iniuria, Iupiter)
4. su-, qu- and gu- before a vowel sound like, and are usually treated as, one consonant : e.g., sua-vis, quin-que 
5. In certain meters two shorts can often substitute for a long. This is called resolution. In metrical schema, resolution is marked thus:

3. Elision

If a word ends in a vowel (e.g., vento), or a vowel + m (e.g., vitam) AND the next word  begins with a vowel or h, the vowel, and the m/h are not scanned and generally not pronounced. This is called elision and is marked thus: vento et. Although it may seem odd, a syllable formed by elision is not necessarily long, as the first, or elided, vowel is not pronounced. 

Examples of elision: 

vento et reads and scans as “vent’et”dicere hos as “dicer’os”

There are a few rare instances in which the rules of elision are modified:

1. If the syllable ending in –m is long by nature, it often will not be elided.
2. Hiatus happens when elision ought to occur, but doesn’t.
3. If the second word is est, the e in est is elided instead of the final vowel or –m syllable. This is called prodelision; e.g., tuum est elides as tuum’st
4. The rules of elision are looser in early Latin poetry (e.g., Plautus or Ennius) or in authors imitating that style (e.g., Cicero).

4. Example. Here’s the first line of the Aeneid, scanned:

A complete guide to Latin Metrics is available in AG §607-626.