FOURTH DECLENSION
[*] 88.
The Stem of nouns of the Fourth Declension ends in
u-. This is usually weakened to
i before
-bus. Masculine and Feminine nouns form the
nominative by adding
s; Neuters have for nominative the simple
stem, but with
ū (long).
[*] 89.
Nouns of the Fourth Declension are declined as follows:
Gender in the Fourth Declension
[*] 90.
Most nouns of the Fourth Declension in
-us
are Masculine.
Exceptions: The following are Feminine:
acus
,
anus,
colus
,
domus
,
īdūs (plural),
manus
,
nurus,
porticus
,
quīnquātrūs
(plural),
socrus
,
tribus
, with a few names of plants and trees. Also, rarely,
penus
,
specus
.
[*] 91.
The only Neuters of the Fourth Declension are
cornū
,
genū
,
pecū
(§ 105.
f),
verū.
1
Case-Forms in the Fourth Declension
[*] 92.
The following peculiarities in case-forms of the Fourth Declension
require notice:—
[*] a.
A genitive singular in
-ī (as
of the second declension) sometimes occurs in nouns in
-tus: as,
senātus
, genitive
senātī
(regularly
senātūs
).
[*] b.
In the genitive plural
-uum is sometimes
pronounced as one syllable, and may then be written
-um: as,
“
currum
”
(Aen. 6.653)
for
curruum
.
[*] c.
The dative and ablative plural in
-ŭbus are retained in
partus
and
tribus; so
regularly in
artus
and
lacus
, and occasionally in other words;
portus
and
specus
have both
-ubus and
-ibus.
[*] d.
Most names of plants and trees, and
colus,
distaff, have also forms of the
second declension: as,
fīcus,
fig, genitive
fīcūs
or
fīcī.
[*] e.
An old genitive singular in
-uis or
-uos and an old genitive plural in
-uom occur rarely: as,
senātuis,
senātuos;
fluctuom.
[*] f.
The ablative singular ended anciently in
-ūd (cf. § 43. N. 1): as,
magistrātūd.
[*] 93.
Domus (F.),
house, has
two stems ending in
u- and
o-. Hence it shows forms of both the fourth
and second declensions:
[*] 94.
Most nouns of the Fourth Declension are formed from verb-stems, or
roots, by means of the suffix
-tus
(
-sus) (§ 238.
b):
-
cantus,
song, CAN, canō, sing;
cāsus
(for †
cad-tus
), chance, CAD,
cadō
,
fall,
exsulātus,
exile, from exsulō, to be an
exile (
exsul
).
[*] a.
Many are formed either from verb-stems not in use, or by
analogy:
-
cōnsulātus
(as if from
†cōnsulō,
-āre),
senātus
,
incestus
.
[*] b.
The accusative and the dative or ablative of nouns in
-tus (
-sus）
form the Supines of verbs (§ 159.
b): as,
spectātum
,
petītum;
dictū,
vīsū
.
[*] c.
Of many verbal derivatives only the ablative is used as a noun: as,
iussū (
meō
),
by (
my）
command; so
iniussū (
populī
),
without (
the
people's)
order. Of some only the dative is
used: as,
dīvīsuī
.
