Latin from scratch #4.11: The third declension of nouns

In the eleventh class of the Latin from Scratch course, we’ll study the third declension, the most complex but probably the most prolific. That’s why it is so important to master it already. Also, what we’re about to learn now will be necessary for the 3rd declension adjectives.

I explain everything in the following video (⏳ 18m 06s ⌛):

Morphology of the third declension

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The third declension is divided into two big groups. We can quickly classify a 3rd declension noun by looking at the statement:

• consonant-stem: nouns with a different amount of syllables between the nominative and the genitive (e.g. mi‑les, mi‑li‑tis)
• i-stem: nouns with the same amount of syllables (e.g. ci‑vis, ci‑vis)

However, there are exceptions where the rules are the opposite:

• consonant-stem (but look like i-stem): mater, matris; frater, fratris; pater, patris
• i-stem (but look like consonant-stem): nouns whose nominative singular ends in 2 or more consonants and whose genitive singular has 2 consonants right before ‑is (e.g. mons, montis; urbs, urbis; pars, partis)

The distinction between these two groups is relatively important, since there are some different endings.

Consonant-stem

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Masculine and feminine nouns are declined the same, whereas neuter nouns have some already known particularities.

Precisely because of these particularities, it is important to quickly identify neuter nouns, which meet one of the following criteria:

• nominative singular in ‑men (e.g. carmen, carminis; flumen, fluminis)
• nominative singular in ‑us and genitive singular in ‑eris, ‑oris or ‑uris (e.g. vulnus, vulneris; corpus, corporis; ius, iuris); not to be confused with 2nd or 4th declension nouns, which can also end in ‑us!
• dental-stem (d, t) with a nominative not ending in ‑s (e.g. caput, capitis; cor, cordis; lac, lactis)

In the following four tables, you have to take into account that the nominative and vocative (and accusative neuter) singular do not have an ending of their own; instead, each specific word has its own ending for those cases.

Masculine-feminine declension

nom. sg.	homo	nom. pl.	hominēs
voc. sg.	homo	voc. pl.	hominēs
ac. sg.	hominĕm	ac. pl.	hominēs
gen. sg.	hominĭs	gen. pl.	hominŭm
dat. sg.	hominī	dat. pl.	hominĭbus
ab. sg.	hominĕ	ab. pl.	hominĭbus

Neuter declension

nom. sg.	caput	nom. pl.	capită
voc. sg.	caput	voc. pl.	capită
ac. sg.	caput	ac. pl.	capită
gen. sg.	capitĭs	gen. pl.	capitŭm
dat. sg.	capitī	dat. pl.	capitĭbus
ab. sg.	capitĕ	ab. pl.	capitĭbus

i-stem

The i-stem declension is not so common in nouns, but it is widely used in adjectives.

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Also this group has masculine-feminine and neuter paradigms. To find out what nouns are neuter, we should look at the nominative singular: they end in ‑e (e.g. mare, maris; rete, retis). However, many of them have lost this ‑e, which makes them look like consonant-stem; we know they are i-stem because the nominative ends in ‑al or ‑ar, as long as they don’t refer to persons (e.g. animal, animalis; vectigal, vectigalis; exemplar, exemplaris).

Masculine-feminine declension

nom. sg.	hostis	nom. pl.	hostēs
voc. sg.	hostis	voc. pl.	hostēs
ac. sg.	hostĕm	ac. pl.	hostēs (-is)
gen. sg.	hostĭs	gen. pl.	hostiŭm
dat. sg.	hostī	dat. pl.	hostĭbus
ab. sg.	hostĕ	ab. pl.	hostĭbus

The accusative plural is most often ‑ēs, but it can appear as ‑is.

Neuter declension

nom. sg.	mare	nom. pl.	mariă
voc. sg.	mare	voc. pl.	mariă
ac. sg.	mare	ac. pl.	mariă
gen. sg.	marĭs	gen. pl.	mariŭm
dat. sg.	marī	dat. pl.	marĭbus
ab. sg.	marĭ	ab. pl.	marĭbus

That’s most of the theory we need to know about the third declension. Now let’s learn its adjectives.

Next: The third declension of adjectives →