121. COMPENSATIVE LENGTHENING. When certain groups of consonants are
simplified by the dropping of a consonant, its time is absorbed by a
preceding short vowel, which thereby becomes long. This is called
_Compensation_. In many cases compensative lengthening is due to the
loss of a preliterary sonant #s# (170, 2): as,
#cānus#, _gray_, from #*casnus# (cf. #cas-cus#, _very old_). See for
other cases of this lengthening, 170, 5, #quīnī#, for #*quincnī#; 170,
6, #īgnōscō#, for #*in-gnōscō#.
122. INDUCED LENGTHENING. Before certain groups of consonants short
vowels have a tendency to become long: as,
(_a._) The prefixes #in-# and #con-# before #s# or #f# lengthened their
vowels in classical Latin (Cic. _O._ 159): as, #īnsānus#, _mad_;
#īnfēlīx#, _unhappy_; #cōnsuēvit#, _he grew used to_; #cōnfēcit#, _he
accomplished_. Elsewhere also the vowel before #ns# and #nf# appears to
have been lengthened: as, #fōns#, _fountain_; #pēnsus#, _weighty_ (Gell.
9, 6); #forēnsis#, _forensic_; #cēnsor#, _censor_; #mēnsa#, _table_;
#mēnsis#, _mouth_; #Valēns#; #Clēmēns#; the #o# of #īnsons#,
_guiltless_, however, is marked as short by the grammarian Probus.
(_b._) A similar lengthening of the vowel before #nc# followed by #t# or
#s# appears: as, #ūnctus#, _anointed_, from #unguō# (Gell. 9, 6);
#iūnctus#, _joined_, from #iungō# (954), #coniūnx#, _spouse_, genit.
#coniugis# (472); #quīnctus#, _fifth_, whence #quīntus# (170, 4) and
#quīnque#, _five_, derive their #ī#; #sānctus#, _hallowed_.
(_c._) Spellings like SIGNVM, _sign_ (well supported in inscriptions),
and DIGNE, _worthily_ (less well supported) show that #i# was at times
lengthened before #gn#. The grammarian Priscian demands this lengthening
for all vowels preceding the ending #-gnus#, #-gna#, #-gnum#.
(_d._) A lengthened vowel before #r# followed by a consonant is also
certain for some words like #ōrdō#, _order_; #fōrma#, _shape_.
(_e._) Some speakers appear to have lengthened the vowel of prepositions
like #con-#, #sub-#, #ob-#, in the compounds of #iaciō# (104, _c_); as
#ōbicit#. This practice, which is disapproved by Gellius (4, 17),
probably arose from the transfer by analogy of the quantity of the first
syllable in forms like #conieciant# (940) to that of the shortened form.
In the same way the occasional spelling CÓNIV́NX, _spouse_, for
#coniūnx#, may owe its long #ō# to the analogy of #cōiunx#, CÓIVGI
(170, 6).
(_f._) Many verb stems ending in #-g# have a long vowel in the past
participle before the suffix #-to-#: as, #tēctus#, _covered_, from
#tego# (916); #tāctus#, _touched_, from #tangō# (925); #pāctus#,
_fixed_, from #pangō# (925); #fīctus#, _moulded_, from #fingō# (954);
#pīctus#, _painted_, from #pingō#. The evidence for #ā# in #maximus# is
very scanty: one case of A with the apex (29, 3) in a faulty
inscription.
(_g._) Of the induced lengthenings enumerated above, only those given in
(_a._) (_b._) (_f._) seem to have been universal in classical Latin. The
rest appear to have been local peculiarities, which, while making
inroads upon the literary language, never gained full recognition.
123. (1.) ANALOGICAL LENGTHENING. In noun stems in #-o# the stem vowel
is lengthened in the genitive plural #-ōrum# (449, 462), by analogy to
the stems in #-ā# (435): as, #servōrum#, _of slaves_, like #mēnsārum#,
_of tables_. For other cases see 122, _e_.
(2.) METRICAL LENGTHENING. On the lengthening of a vowel (or a syllable)
under the influence of verse-ictus, see 2505.