First declension

The first declension consists of Latin words whose stems end in ·a. First declension nouns are almost always feminine, except for a few words that denote men.

Regular

Regular first declension nouns decline like this:

singular plural
nominative puella puellae
vocative puella puellae
accusative puellam puellas
genitive puellae puellarum
dative puellae puellis
ablative puella puellis

Exceptions

Gender

All the first declension nouns in Oxford Latin Course, Book I, are feminine, except nauta -ae m., sailor.

dea, goddess and filia, daughter

The nouns dea -ae f., goddess and filia -ae f., daughter have irregular dative/ablative plural forms, deabus and filiabus. Therefore:

word dative/ablative plural
deus -i m., god dis
dea -ae f., goddess deabus
filius -i m., son filiis
filia -ae f., daughter filiabus

Aeneas

The name Aeneas -ae m., Aeneas has an irregular nominative singular form: Aeneas. Its other forms are regular, including its vocative singular, Aenea.