Second Declension (Declinatio Secunda)

The circumflex accent ( ˆ ) is used to denote the length of the vowels.

To the Second declension are referred nouns of all the three genders the stems of which ends by -o; it is usually called o-declension.

    The masculines end in Nom. sg. in –us, -er, -ir; the feminines end only by –us; and the neuters end only by –um.

    The masculines of –er are of two types:

• the nouns like puer m boy preserve the -e sound in all their forms, because it makes part of their stem;
• the nouns like ager m field, where the -e sound does not belong to the stem, use it in Nom. sg. and Voc. sg. only to ease pronunciation.

    The neuters have identical forms for Nom., Acc. and Voc. of both Sg. and Pl.
 

Case	Singular
	m	m	m	m	f	n
Nom. Gen. Dat. Acc. Abl. Voc.	populus populi populo populum populo popule	puer  pueri puero puerum puero puer	ager  agri agro agrum agro ager	vir  viri viro virum viro vir	fagus fagi fago fagum fago fage	donum doni dono donum dono donum
	Plural
Nom. Gen. Dat. Acc. Abl. Voc.	populi populôrum populis populos populis populi	pueri puerôrum pueris pueros pueris pueri	agri agrôrum agris agros agris agri	viri virôrum viris viros viris viri	fagi fagôrum fagis fagos fagis fagi	dona donôrum donis dona donis dona

    The nouns of the Second declension are presented in the dictionaries with their Nom. and Gen. sg. form, e.g.

    populus, i m people;
    puer, eri, m boy;
    ager, agri, m field;
    vir, i, m man;
    fagus, i, f beech tree;
    donum, i, n gift.
 

1. The personal names in –ius, -aius, -eius forms Voc. sg. by –i, e.g.

Vergilius : Vergili,
Gaius : Gai,
Pompeius : Pompei.

filius : fili.

3. The noun deus, dei m god have many doublet forms:
 

Case	Singular	Plural
Nom. Gen. Dat. Acc. Abl. Voc.	deus  dei, divi  deo, divo  deum  deo, divo  deus, dive	dei, dii, di  deôrum, deum  deis, diis, dis  deos  deis, diis, dis  dei, dii, di

4. The noun locus, i, m place, seat, (pl.) locality has the forms loci and loca in Nom. and. Voc. pl.

5. Several words ending in –us are of neuter:
    pelagus, i, n sea;
    virus, i, n poison;
    vulgus, i, n crowd.