ABSTRACT
Much as English nouns change their endings to show a plural (farmers , children ), so do Latin nouns. However, as you may have guessed, the Latin ones have more than one plural ending. There is a plural ending for each of the cases:
singular
plural
Nominative
puella
puellae
Vocative
puella
puellae
Accusative
puellam
puellās
Nominative
servus
servī
Vocative
serve
servī *
Accusative
servum
servōs
the vocative plural is identical to the nominative plural for all nouns.