627. A dozen adjectives with stems in #-bri-#, #-cri-#, or #-tri-#, have
a distinctive form in #-er# for the masculine nominative singular; they
are:
celeber, _thronged_
salūber, _healthy_
ācer, _keen_
alacer, _lively_
volucer, _winged_
campester, _of a plain_
equester, _cavalry-_
palūster, _of a swamp_
pedester, _foot-_
puter, _rotten_
silvester, _woody_
terrester, _land-_
So also #celer#, swift. The names of months, #September#, #Octōber#,
#November#, #December#, are also adjectives with stems in #-bri-#, but
are not used in the neuter. Other adjectives with stems in #-bri-#,
#-cri-#, or #-tri-#, have no distinctive form for the masculine
nominative singular: as, #muliebris#, #mediocris#, #inlūstris#.