251. Nearly all adjectives of the third declension have i-stems, and they are declined almost like nouns with i-stems.

252. Adjectives learned thus far have had a different form in the nominative for each gender, as, bonus\, m.; bona\, f.; bonum\, n.  Such an adjective is called an _adjective of three endings_.  Adjectives of the third declension are of the following classes: 

    I. Adjectives of three endings—­
      a different form in the nominative for each gender.

   II.  Adjectives of two endings—­
      masculine and feminine nominative alike, the neuter different.

  III.  Adjectives of one ending—­
      masculine, feminine, and neuter nominative all alike.

253. Adjectives of the third declension in -er have three endings; those in -is have two endings; the others have one ending.

CLASS I

254. Adjectives of Three Endings are declined as follows: 

        a:cer, a:cris, a:cre, keen, eager
        STEM a:cri-
        BASE a:cr-

SINGULAR                PLURAL
MASC.    FEM.     NEUT.    MASC.           FEM.            NEUT. 
Nom.  a:cer   a:cris  a:cre     a:cre:s        a:cre:s        a:cria
Gen.  a:cris  a:cris  a:cris    a:crium        a:crium        a:crium
Dat.  a:cri:   a:cri:   a:cri:     a:cribus       a:cribus       a:cribus
Acc.  a:crem  a:crem  a:cre     a:cri:s, -e:s  a:cri:s, -e:s  a:cria
Abl.  a:cri:   a:cri:   a:cri:     a:cribus       a:cribus       a:cribus

CLASS II

255. Adjectives of Two Endings are declined as follows: 

        omnis, omne, every, all[1]
        STEM omni-
        BASE omn-

SINGULAR                 PLURAL
MASC.  AND FEM.   NEUT.     MASC.  AND FEM.   NEUT. 
Nom.  omnis           omne     omne:s          omnia
Gen.  omnis           omnis    omnium          omnium
Dat.  omni:            omni:     omnibus         omnibus
Acc.  omnem           omne     omni:s, -e:s    omnia
Abl.  omni:            omni:     omnibus         omnibus

    [Footnote 1:  omnis\ is usually translated _every_ in the singular
    and _all_ in the plural.]

CLASS III

256. Adjectives of One Ending are declined as follows: 

        pa:r, equal
        STEM pari-
        BASE par-

SINGULAR                 PLURAL
MASC.  AND FEM.   NEUT.     MASC.  AND FEM.   NEUT. 
Nom.  pa:r            pa:r     pare:s          paria
Gen.  paris           paris    parium          parium
Dat.  pari:            pari:     paribus         paribus
Acc.  parem           pa:r     pari:s, -e:s    paria
Abl.  pari:            pari:     paribus         paribus

  1.  All i-stem adjectives have -i:  in the ablative singular.