419. Nouns have five cases, the _Nominative_, _Genitive_, _Dative_,
_Accusative_, and _Ablative_.
The nominative represents a noun as subject, the accusative as object;
the genitive denotes the relation of _of_, the dative of _to_ or _for_,
and the ablative of _from_, _with_, _in_, or _by_. But the meanings of
the cases are best learnt from reading. All cases but the nominative and
vocative (420) are called _Oblique Cases_.
420. Town names and a few appellatives have also a case denoting the
place where, called the _Locative_. Masculine stems in #-o-# and some
Greek stems with other endings have still another form used in
addressing a person or thing, called the _Vocative_.
421. The stem of a noun is best seen in the genitive; in the genitive
plural it is preserved without change, except that #o# of #-o-# stems is
lengthened (123). In dictionaries the stem ending is indicated by the
genitive singular, thus: #-ae#, #-ī#, #-is#, #-ūs# (#-ĕī#), indicate
respectively stems in #-ā-#, #-o-#, a consonant or #-i-#, #-u-#, and
#-ē-#, as follows: