Second Declension Forms – Masculine
Most second declension masculine nouns have a –us or –er ending in the nominative singular. This makes them easy to identify in contrast to the typical –a ending of the first declension. However, the second declension has its own characteristic inflections. Although the rules for forming the inflections is similar to the first (i.e. base + ending), the endings themselves are different. A typical masculine, second-declension noun has the following forms:
Notice that unlike the first declension, the genitive and dative singular forms are different. This makes their identification easier in a sentence. Also notice that the plural dative and accusative have the same –is form as the first declension. The genitive plural is similar in form to the first declension (–orum versus –arum) and the accusative singular also has a similar form (–um versus –am).
Unfortunately for the beginning Latin student, the genitive singular and the nominative plural have the same form. Only the context, and occasionally word order, will determine what its use is in a sentence. This is also true for the dative and ablative singular forms.
Some second declension nouns end in –er but their forms follow the same rules as those ending in –us. For example:
nom. Puer (Amicus)
gen. Pueri (Amici)
dat. Puero (Amico)
acc. Puerum (Amicum)
abl. Puero (Amico)
nom. Pueri (Amici)
gen. Puerorum (Amicorum)
dat. Pueris (Amicis)
acc. Pueros (Amicos)
abl. Pueris (Amicis)
However, some masculine nouns ending in –er retain the –e (as in puer) while others drop the –e (as in ager, agri). Also, the often-used word vir, viri has the uncommon –ir ending which must be memorized to properly decline this word.