[Footnote A:  The genitive plural ending -ium is written to mark
    the i-stems.]

    [Footnote B:  The genitive plural of mare\ is not in use.]

241. To decline a noun of the third declension correctly we must know whether or not it is an i-stem.  Nouns with i-stems are

  1.  Masculines and feminines: 

    a. Nouns in -e:s and -i:s with the same number of syllables in
    the genitive as in the nominative.  Thus caede:s, caedis\, is an
    i-stem, but mi:les, mi:litis\, is a consonant stem.

    b. Nouns in -ns and -rs.

    c. Nouns of one syllable in -s or -x preceded by a consonant.

  2.  Neuters in -e, -al, and -ar.

242. The declension of i-stems is nearly the same as that of consonant stems.  Note the following differences: 

a. Masculines and feminities have -ium in the genitive plural and -i:s or -e:s in the accusative plural.

b. Neuters have -i:  in the ablative singular, and an -i- in every form of the plural.

243. Masculine and Feminine I-Stems.  Masculine and feminine i-stems are declined as follows: 

caede:s, f.,  hostis,      urbs, f.,  clie:ns, m.,
slaughter   m., enemy  city     retainer
STEMS  caedi-        hosti-       urbi-      clienti-
BASES  caed-         host-        urb-       client-

SINGULAR TERMINATIONS
M. AND F.
Nom. caede:s hostis urbs clie:ns[1] -s, -is,
or -e:s
Gen. caedis hostis urbis clientis -is
Dat. caedi:  hosti:  urbi:  clienti:  -i: 
Acc. caedem hostem urbem clientem -em (-im)
Abl. caede hoste urbe cliente -e (-i:)

PLURAL
Nom.   caede:s       hoste:s      urbe:s     cliente:s      -e:s
Gen.   caedium       hostium      urbium     clientium      -ium
Dat.   caedibus      hostibus     urbibus    clientibus     -ibus
Acc.   caedi:s,      hosti:s,     urbi:s,    clienti:s,     -i:s,
-e:s          -e:s         -e:s       -e:s           -e:s
Abl.   caedibus      hostibus     urbibus    clientibus     -ibus

[Footnote 1:  Observe that the vowel before -ns is long, but that
it is shortened before -nt.  Cf.  Sec. 12.2, 3.]

1. avis\, ci:vis\, fi:nis\, ignis\, navis\ have the ablative
singular in -i:  or -e.

2. turris\ has accusative turrim\ and ablative turri:\ or turre\.

244. Neuter I-Stems.  Neuter i-stems are declined as follows: