114. HIATUS. A succession of two vowel sounds not making a diphthong is
called _Hiatus_.
When in the formation of words by means of suffixes or prefixes or
through the loss of an intervening consonant, two vowels come into
contact within a word we speak of _internal hiatus_; the term _external
hiatus_ comprises those cases where, in connected discourse, the final
vowel of one word comes into contact with the initial vowel of the
following word. For the latter kind, see 2474.
115. The treatment of vowels in internal hiatus is four-fold: (1.) The
hiatus may remain; (2.) the two vowels may be fused into one
(_Contraction_); (3.) one of the two vowels may be dropped (_Elision_);
and (4.) the two vowels may be combined into a diphthong.
116. HIATUS is maintained (_a._) between two adjacent vowels the second
of which is long and accented (according to the classical accentuation):
as, #coḗgi#, _I forced_, and #coā́ctus#, _forced_ (937); but #cōgō#
(118, 3). For #coepi#, instead of #coḗpī#, _I began_, see 120.
(_b._) In many prepositional compounds when the members were still felt
to be independent: as, #praeesse# (the contracted form #praesse# is
found in inscriptions); #dēerunt#, _they will be wanting_, by the side
of #dērunt#; #coalēscō#, _grow together_ (the contracted form #cōlēscō#
appears in Varro); #cooptāre#, _coöpt_, #cooperiō#, _I cover up_ (by the
side of rare #cōptāre#, #cōperīre#); #coïtus#, _meeting_, by the side of
#coetus# (120).
(_c._) A comparatively large number of vowel combinations remain
unchanged: as #ea# and #eā# in #eam#, _her_, and #meā#, _by my_ (fem.
sing.); #ia# and #iā# in #māria#, _seas_, #viātōris#, _of the
traveller_; #ua# and #uā# in #bēlua#, _monster_, #suā#, _through her_
(fem. sg.); #iē# in #quiēs#, _quiet_; #uē# in #luēs#, _pestilence_; #eī#
in #meī#, _of me_; #uī# in #tuī#, _of thee_; #eō# in #meō#, _by my_
(masc. sing.).
117. SYNIZESIS. In these combinations the first vowel is sometimes made
unsyllabic (83). This is called _synizesis_ (2499) and is not rare in
poets, being often the only means of adapting a word to the requirements
of certain metres. Thus, #fortuītus# (- ⏑ - ⏓) must appear in a
hexameter as #fortvītus# (#fortṷītus#). See 2499, 2503.
118. CONTRACTION. (1.) Two like vowels may unite in one long vowel;
rapidity of utterance was favourable to such fusion. In compounds, the
desire to keep the members distinct often prevented it. So always
#nēmō#, _nobody_, for #*neemō# from #*ne-hemō#, _no man_ (for the loss
of #h#, see 58, 150; for #e# in #*hemō#, see 144); and by the side of
the open forms, #nīl# from #nihil#, _nothing_; #vēmēns# from #vehemēns#,
_rapid_ (connected with the verb #vehō#); rarely #dērunt#, _they will be
wanting_, and #dēsse#, _to be wanting_, for #dēerunt#, #dēesse#;
#dēlēram#, _I had destroyed_, from #*dēlēeram# for #dēlēveram# (for the
loss of #v#, see 153), see 890; #passūm#, _of paces_, for #passuum#
(591).
(2.) A diphthong absorbs the following vowel: as, #praetor#, older
#praitor#, _praetor_, from #*prai-itor#, _who goes before_; inscriptions
show #praerunt# for #praeerunt#, _they will be before_; for #praebēre#,
_to furnish_, the open form #praehibēre# occurs in Plautus (1004).
(3.) If two unlike vowels are contracted at all, they usually unite in
the long sound of the first vowel. Thus, #o# and #a# yield #ō#: as,
#cōgō#, _I force_, from #co-agō#; #cōgitō#, _I think_, from #co-agitō#.
Similarly Varro has #cōlēscat#, _it may combine_, for #co-alēscat#. #o#
and #e# yield #ō#: as, #prōmō#, _bring out_, #cōmō#, _put up_, for
#pro-emō#, #co-emō# (953). #ē# and #a# yield #ē#: as, #dēgō#, _I pass
away_, from #dē-agō# (937). #i# and #e# in the termination of the
vocative of #-io-# stems probably contracted to #-ī#; as #fīlī# from
#*fīlie#, 459. But in denominative (365) and other verbs of the first
conjugation #ā# and #ō# contract into #ō#: as, #amō#, _I love_, from
#*amā-ō# (cf. Greek τιμά·ω); and #ā# and #ē# into #ē#: as, #amēs#, _thou
mayest love_, for #*amā-ēs#.
119. ELISION. Only rarely the first of two successive vowels is dropped:
as, #nūllus#, _no_, for #*ne-ūllus#; likewise the final vowel of the
first member of nominal compounds: as, #multangulus#, _with many
corners_, for #*multi-angulus# (cf. #multi-cavus#, _with many holes_);
#flexanimus#, _heart-rending_, for #*flexi-animus# (cf. #flexi-pēs#,
_with bent feet_).
120. COMBINATION INTO DIPHTHONGS. The union of two successive vowels
into a diphthong is equally rare: #o# and #i# are combined to #oi#,
#oe#, in #coetus#, _meeting_, by the side of the open form #coïtus#
(116, _b_); the perfect #coepī# (812), _I began_, owes its diphthong
#oe# to forms in which the #e# was short and unaccented, such as the
rare present forms #coepiō# for #có-ĕpiō# (813); for #coḗpi# (813, 863)
would have remained unchanged (116, _a_). #neuter#, with the accent on
the #e#, was pronounced as three syllables, later #eu# became
diphthongal; #neutiquam# with synizesis (117) of #e#. #e# and #ī̆#
sometimes contract to #e͡i# in #rēi# (601, 602) and in #de͡inde#, #dēin#
in the classic poets.