Nouns and adjectives in some languages vary according to their number, gender and case. This is called declension. School children often had to decline a noun out loud, listing its various forms. For example, to decline the plural of the Latin word puella (girl) you would recite: puellae, puellae, puellas, puellarum, puellis, puellis.
To learn more about the meaning of the Latin declensions, click here.