(3) The last consonant of some roots is assimilated to t of the suffixes.
(4) Strengthening of the first vowel sometimes takes place before these.

(a) "-tu.m" with an additional i
pacA + i + tu.m = pacitu.m (to cook)
khaadA + i + tu.m = khaaditu.m (to eat)
harA + i + tu.m = haritu.m (to carry)
dhaavu + i + tu.m = dhaavitu.m (to run)

(i) added to the bases
su.na + i + tu.m = su.nitu.m (to hear)
bujjha + i + tu.m = bujjhitu.m (to understand)
jaana + i + tu.m = jaanitu.m (to know)
chinda + i + tu.m = chinditu.m (to cut)

(b) after the roots ending in aa
daa + tu.m = daatu.m (to give)
paa + tu.m = paatu.m (to drink)
.thaa + tu.m = .thaatu.m (to stand)
~naa + tu.m = ~naatu.m (to know)
yaa + tu.m = yaatu.m (to go)

Root kara becomes kaa before these; then it is treated as a root
ending in aa.
kaa + tu.m = kaatu.m (to do)
kaa + tava = kaatave (to do)

(c) where assimilation occurs and the radical vowel is strengthened
karA + tu.m = kattu.m (to do)
chidA + tu.m = chettu.m (to cut)
bhujA + tu.m = bhottu.m (to eat, to enjoy)
padA + tu.m = pattu.m (to arrive or attain)
harA + tu.m = hattu.m (to carry)
vadA + tu.m = vattu.m (to say)
gamU + tu.m = gantu.m (to go)
labhA + tu.m = laddhu.m (to get)
budhA + tu.m = boddhu.m (to perceive)

In the last two examples both bh+t and dh+t have become ddh.

(d) where "t" is not doubled and strengthening of the vowel takes place
nii + tu.m = netu.m (to lead or carry)
ji + tu.m = jetu.m (to conquer)
su + tu.m = sotu.m (to hear)
huu + tu.m = hotu.m (to be or become)

156. To the causal bases, and the bases of the seventh conjugation,
ending in a, these suffixes are joined with the help of an i. They are
directly added to those bases ending in e.

Causal bases
kaare + tu.m = kaaretu.m,
kaaraya + i + tu.m = kaarayitu.m (to cause to do)
maaraape + tu.m = maaraapetu.m,
maaraapaya + i + tu.m = maaraapayitu.m (to cause to kill)
gaahe + tu.m = gaahetu.m,
gaahaapaya + i + tu.m = gaahaapayitu.m (to cause to take)

Bases of the seventh conjugation
core + tu.m = coretu.m,
coraya + i + tu.m = corayitu.m (to steal)
paale + tu.m = paaletu.m,
palaya + i + tu.m = paalayitu.m (to protect or govern)
dese + tu.m = desetu.m,
desaya + i + tu.m = desayitu.m (to preach)