180. The following synopsis shows the forms of the verb amō, a regular verb of the 1st conjugation, arranged according to the three stems (§ 164).
181. In tenses formed upon the Perfect Stem, v between two vowels is often lost and contraction takes place.
a. Perfects in -āvī, -ēvī, -ōvī, often contract the two vowels into ā, ē, ō, respectively.
amāsse for amāvisse
amārim for amāverim
amāssem for
amāvissem
cōnsuērat for cōnsuēverat
flēstis for flēvistis
nōsse for nōvisse
So, also, in Perfects in -vī, where the v is a part of the Present stem.
commōrat for commōverat
Note— The 1st person of the Perfect Indicative (as, amāvī) is never contracted, the 3rd very rarely.
b. Perfects in -īvī regularly omit v, but rarely contract the vowels except before st and ss, and very rarely in the 3rd person Perfect.
audieram for audīveram
audīsse for audīvisse
audīstī for
audīvistī
abiit for abīvit
abiērunt for abīvērunt
Note 1— The forms sīris, sīrit, sīrītis, sīrint, for sīveris etc. (from sīverō or sīverim), are archaic.
Note 2— In many forms from the Perfect stem -is-, -iss-, -sis-, are lost in like manner, when s would be repeated if they were retained.
dīxtī for dīxistī
(x = cs)
trāxe for trāxisse
ēvāstī for ēvāsistī
vīxet
for vīxisset
ērēpsēmus for ērēpsissēmus
dēcēsse for dēcessisse
These forms belong to archaic and colloquial usage.
182. Four verbs—dīcō, dūcō, faciō, ferō—with their compounds, drop the vowel termination of the Imperative, making dīc, dūc, făc, fĕr; but compounds in -ficiō retain it (cōnfice).
Note— The Imperative forms dīce, dūce, face (never fere), occur in early Latin.
a. For the Imperative of sciō, the Future form scītō is always used in the singular, and scītōte usually in the plural.
183. The following ancient forms are found chiefly in poetry:
faxim, faxō
iussō
recēpsō (= fēcerim etc.)
ausim (= ausus sim)
vocārier for vocārī
agier for agī
amāssis from amō
levāssō from levō
impetrāssere from impetrō
iūdicāssit from iūdicō
Cf. § 263.2.b, Note