dea

Dea, deae is feminine, first declension, built to match deus. Its one irregularity is the dative and ablative plural deabus rather than deis, and it exists for a practical reason: prayers regularly address "dis deabusque", the gods and the goddesses, and the formula falls apart if both words come out as deis. Filiabus does the same work against filiis.

Latin also uses diva for a goddess, especially in verse and for deified empresses, and that is the word Italian took for an opera singer. Dea has nothing to do with dies despite the look of the fifth-declension forms; the resemblance is an accident of a short word. French deesse and Spanish diosa both descend from it.