The scientific suffix -idae is used to form names of subclasses of plants or families of animals, e.g. Bovidae. In scientific writing (in English and German), the resulting words are treated as plural nouns. Also, it appears to be a regular first declension nominative plural, so I at first interpreted it as feminine and assumed a nominative singular -ida or maybe Greek-type -idē.

According to Wiktionary, it is derived from the Ancient Greek suffix -ίδης but has been interpreted by some to instead be a transcription of -ειδής. Both pages claim a Latin suffix -idēs as their descendant, which forms masculine nouns. But, according to Wiktionary, that suffix is treated as third declension, so that -idēs cannot ever yield the plural -idae. Following that etymology, I would have assumed masculine Greek-type first declension, analogous to comētēs, comētae, which does yield -ae as a nominative plural ending and thus would fit.

The person who coined the scientific suffix apparently didn't write in Latin, so he probably hasn't answered the question himself.

Currently I am torn between treating it as feminine -ida(/-idē), -idae or masculine -idēs, -idae. I lean toward the latter declension because of the etymology, but I am undecided because of the unexpected gender and lack of precedent (that I know of).

So, what is its gender and singular declension? Are singular forms or combinations with adjectives attested anywhere in scientific Latin or is there a pre-existing suffix in Latin writing of any era that would fit (maybe use of -idēs as a suffix resulting in first declension nouns or adjectives)?

  • 1
    The Wikipedia page lists Monographia Apum Angliae as William Kirby's first major work, so maybe he did write in Latin.
    – Ben Kovitz
    Commented Mar 28, 2023 at 8:48
  • 1
    I followed Wikipedia's link to the full work. Sadly, only the title is in Latin. The work itself is in English.
    – Lukas G
    Commented Mar 29, 2023 at 9:09

2 Answers 2


Declension of patronymics in Latin as an actual language

The Wiktionary entry on -idēs is incomplete (leading you to the mistaken impression that -idēs cannot ever yield the plural -idae): first-declension forms are definitely possible (as in "Tyndaridae" used by Cicero in the phrase "Tyndaridae fratres" where it's clear it's a masculine plural patronymic) (Tusculanae Disputationes 1.28.7).

In Classical Latin, Greek masculine nouns ending in ης could be partially adapted to either the first or third declension (or even, in the genitive case, to the second declension). Here is a question I asked about words ending like this: How are "Arsaces" and "Gotarzes" declined, and why?

The Zumpt passage I quoted there implies that patronymics are less likely than other ης names to be adapted to the third declension. However, I'm not sure about this. My understanding is that the names Εὐριπίδης and Ἀλκιβιάδης are patronymic in form (although the patronymic force of the ending was lost), and in Latin, Euripides and Alcibiades frequently have third-declension forms in accusative -em or genitive -is. Maybe Zumpt's qualification that third-declension inflection is common "if not patronymics" refers only to words with patronymic force (in which case it seems arguable whether taxon names would qualify). In any case, even if third-declension inflection is possible, first-declension inflection is not impossible for Latin words ending in the Greek suffix -idēs.

The ending -idae in scientific "Latin"

Although scientific nomenclature is theoretically supposed to follow Latin grammar (at least in certain areas), in practice it often doesn't. The sometimes-substantial distance between scientific nomenclature and actual Latin makes it a bit dubious in my opinion to try to come up with singular or plural versions of scientific names for taxa.

However, if you have some reason to form a singular version of the scientific ending -idae, I agree with Tuomo Sipola's answer that masculine -ides is the way to go.

  • I am probably going to accept this excellent answer as it details exactly what I was looking for and gives precedent for the original suffix’ use in Classical Latin. But I will wait for another day or two in order to leave opportunity for answers that find precedent of nouns suffixed with -idae in the modern sense being declined or given a discernible gender in scientific writing.
    – Lukas G
    Commented Nov 26, 2021 at 15:34

I think it is the patronymic -ides, which is in the first declension in Latin. The plural forms are regular, so bovidae 'sons of a cow' would be bovides in the singular. It would be a masculine noun.

Compare to cometes, gen. cometae, which is cometae, gen. cometarum in the plural.

See Allen and Greenough, 1st Declension: Greek Nouns: https://dcc.dickinson.edu/grammar/latin/1st-declension-greek-nouns

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