461. In the nominative plural masculine, #-ei# sometimes occurs (465):
as, #nātei geminei#, _twins born_ (Plaut.); #-eis# or #-īs# is rare
(465): as, #Sardeis#, _Sardians_; #oculīs#, _eyes_; not infrequently
#hīsce#, _these here_ (Plaut.); masculine stems in #-io-# have rarely a
single #-ī#: as, #fīlī#, _sons_. For #-āī#, #-ēī#, or #-ōī#, see 458.
The nominative and accusative plural of neuters ended anciently in #-ā#
(130, 2). But #-ā# was shortened at an early period.
462. In the common genitive plural #-ōrum#, the #-o-# of the stem is
lengthened (123). A genitive plural in #-ū̆m# (or, after #v#, in #-ŏ̄m#)
is common from #dīvos#, #dīvus#, and #deus#, _god_; from #dēnārius#,
_denar_, #modius#, _peck_, #nummus#, _money_, #sēstertius#, _sesterce_,
and #talentum#, _talent_, with numerals; and from cardinals and
distributives (641): as, #dīvŏ̄m#, #divū̆m#, #deū̆m#; #mīlle
sēstertiŭm#; #ducentū̆m#; #bīnŭm#. The #u# was originally long (132);
but it was shortened before 100 A.D.
463. Other masculine substantives have occasionally this genitive: as,
#līberū̆m#, _of children_; particularly in set phrases and in verse: as,
#centuria fabrū̆m#, _century of mechanics_; #Graiū̆m#, _of Greeks_. With
neuter substantives, as #oppidū̆m#, for #oppidōrum#, _of towns_, and
with adjectives it is rare.
464. In the dative and ablative plural, #-eis# is rare (98): as,
#Epidamnieis# (Plaut.). Stems in #-io-# have rarely a single #ī#: as,
#fīlīs#, _for sons_. For #-āīs#, #-ēīs#, or #-ōīs#, see 458. #ambō#,
_both_, and #duo#, _two_, have #ambōbus# and #duōbus# (640).