Usage notes
Latin genitive plural forms take the ending -um either by itself, or with additional preceding material (generally determined by the word's conjugation class). First and second declension nouns and adjectives usually have genitive plural forms ending in -ārum and -ōrum, but some words can take the short ending -um (without preceding -ār-/-ōr-) instead: this is common with words denoting weights, measures and monetary value and with distributive numerals.[1][2]
- In the second declension, the genitive plural in -um can be found:
- In the first declension, the genitive plural in -um can be found:
- in the Greek-derived measure words amphora and drachma (less frequently than drachmārum)
- in dactylic verse, in compounds of -cola and -gena
- in dactylic verse, in some masculine Greek proper nouns, such as patronymics
The spelling -ûm (or -ôm after V/U), introduced in the Renaissance, is used in some New Latin texts for forms such as amphorûm and deûm. These were incorrectly interpreted as contractions of amphorārum and deōrum, and as a result, it was assumed that genitive plural deum ended in -ūm (with a vowel long by nature) in contrast to accusative singular deum (ending in -ŭm, with a vowel short by nature). Compare the use of the circumflex in New Latin to distinguish the ablative ending -â (with long ā) from the nominative/vocative ending -a (with short ă) in first declension singular nouns, or to mark third-person plural perfect forms ending in -ēre, which was assumed to be a "contracted" form of the alternative ending -ērunt (e.g. fuêre, taken to be a contraction of fuerent[3]). However, the assumed distinction between deûm with long ū and deum with short ŭ is outdated: according to modern etymological understanding, all Latin words ending in -um, regardless of their case, number or declension, were pronounced in Classical Latin with a short vowel in the final syllable.[4][5] Rather than being contractions, second-declension genitive plural forms in -um such as deum are archaisms showing the original Proto-Indo-European inflection pattern for nouns of this this declension.
Third declension words that have genitive plurals ending in -um as an alternative to -ium have also been spelled with -ûm, again with the justification that the shorter ending is interpreted as being a contraction of the longer variant.[6] Examples are coelestûm and caedûm used as spellings of the short genitive plurals of coelestis and caedes (compared to the long forms coelestium and caedium).[7]
Aside from the contraction hypothesis, the use of the circumflexed spelling -ûm may additionally have been influenced by the use of the circumflex in the spelling of Greek genitive plural forms ending in -ῶν.[8]