The principal Italo-Celtic forms are: • the
thematic genitive singular in
ī (e.g. Latin second declension
dominus, gen.sg.
dominī). Both in Italic (
Popliosio Valesiosio,
Lapis Satricanus) and in Celtic (
Lepontic -oiso,
Celtiberian -o), traces of the
-osyo genitive of
Proto-Indo-European (PIE) have also been discovered, which might indicate that the spread of the
ī genitive occurred in the two groups independently (or by areal diffusion). The
ī genitive has been compared to the so-called
Cvi formation in
Sanskrit, but that too is probably a comparatively late development. The phenomenon is probably related to the feminine long
ī stems and the
Luwian i-mutation. • the formation of
superlatives with reflexes of the PIE suffix *
-ism̥mo- (Latin
fortis,
fortissimus "strong, strongest", Old Irish
sen,
sinem "old, oldest", Oscan
mais,
maimas "more, most"), where branches outside Italic and Celtic derive superlatives with reflexes of PIE *
-isto- instead ( "broad, broadest", "beautiful, fairest",
Old Norse rauðr,
rauðastr "red, reddest", as well as English "-est"). • the
ā-subjunctive. Both Italic and Celtic have a subjunctive descended from an earlier optative in
-ā-. Such an optative is not known from other languages, but the suffix occurs in
Balto-Slavic and
Tocharian past tense formations, and possibly in
Hittite -ahh-. • the collapsing of the PIE
aorist and
perfect into a single
past tense. In both groups, this is a relatively late development of the proto-languages, possibly dating to the time of Italo-Celtic language contact. • the assimilation of *p to a following *kʷ. This development obviously predates the Celtic loss of *p: • PIE *pekʷ- 'cook' →
Latin coquere;
Welsh pobi (Welsh p is from Proto-Celtic *kʷ) • PIE *penkʷe 'five' → Latin
quīnque; Old Irish
cóic, Welsh
pump • PIE *perkʷu- 'oak' → Latin
quercus;
Goidelic ethnonym
Querni, in northwest Hispania
Querquerni A number of other similarities continue to be pointed out and debated. The
r-passive (
mediopassive voice) was initially thought to be an innovation restricted to Italo-Celtic until it was found to be a retained archaism shared with Hittite, Tocharian, and possibly the
Phrygian language. == References ==