Obstruents

• Palatovelars merged with plain velars, a change termed centumization.
  • *ḱ > *k
  • *ǵ > *g
  • *ǵʰ > *gʰ
  • Sequences of palatovelars and *w merged with labiovelars: *ḱw, *ǵw, *ǵʰw > *kʷ, *gʷ, *gʷʰ
• *p...kʷ > *kʷ...kʷ, a change also found in Celtic.
• Labiovelars lose their labialisation before a consonant: *kʷC, *gʷC, *gʷʰC > *kC, *gC, *gʰC.
• Obstruent consonants become (unaspirated) voiceless before another voiceless consonant (usually *s or *t).
• Voiced aspirates become fricatives. Word-initially, they become voiceless, while they are allophonically voiced word-medially. Judging from Oscan evidence, they apparently remained fricatives even after a nasal consonant. In most other Italic languages they developed into stops later in that position.
  • *bʰ > *f (medially *β)
  • *dʰ > *θ (medially *ð)
  • *gʰ > *x (medially *ɣ)
  • *gʷʰ > *xʷ (medially *ɣʷ)
• *s was also allophonically voiced to *z word-medially.^[5]
• *sr, *zr > *θr, *ðr.^{[clarification needed]}
• *θ, *xʷ > *f. Found in Venetic vhagsto/hvagsto (compare Latin faciō). The voiced allophones *ð and *ɣʷ remained distinct from *β in Latin and Venetic, but also merged in Osco-Umbrian.
• *tl > *kl word-medially.^[5]
• Final *t became *d ^[6]

Vowels and sonorants

• *l̥, *r̥ > *ol, *or^[7]
• *m̥, *n̥ > *əm, *ən (see below on "Vowels")
• *j is lost between vowels. The resulting vowels in hiatus contract into a long vowel if the two vowels are the same.
• *ew > *ow.^[7]
• *o > *a before labials and *l.
• *-mj- > -*nj- ^[8]

Laryngeals

The laryngeals are a class of hypothetical PIE sounds *h₁, *h₂, *h₃ that usually disappeared in late PIE, leaving coloring effects on adjacent vowels. Their disappearance left some distinctive sound combinations in Proto-Italic. In the changes below, the # follows standard practice in denoting a word boundary; that is, # at the beginning denotes word-initial.^[9] H denotes any of the three laryngeals.

The simpler Italic developments of laryngeals are shared by many other Indo-European branches:

• *h₁e > *e, *h₂e > *a, *h₃e > *o
• *eh₁ > *ē, *eh₂ > *ā, *eh₃ > *ō
• *H > *a between obstruents
• Laryngeals are lost word-initially before a consonant.

More characteristic of Italic are the interactions of laryngeals with sonorant consonants. Here, R represents a sonorant, and C a consonant.

• #HRC > #aRC and CHRC > CaRC, but #HRV > #RV
• CRHC > CRāC, but CRHV > CaRV
• CiHC and probably CHiC > CīC

Morphology

• General loss of the dual, with only a few relics remaining.^[10]
• Loss of the instrumental case.^[10]

Consonants

• [ŋ] was an allophone of /n/ before a velar consonant.
• The voiced fricatives [β], [ð], [ɣ], [ɣʷ] and [z] were in complementary distribution with word-initial voiceless fricatives [ɸ], [θ], [x], [xʷ] and [s], and were thus originally simply allophones of each other. However, at some point in the Proto-Italic period, the allophony was somewhat disrupted by the loss of the voiceless allophones [θ] and [xʷ], which merged with [ɸ]. Scholars^[who?] disagree on whether to reconstruct Proto-Italic with the phonemes /θ ~ ð/ and /xʷ ~ ɣʷ/ still present (hence assuming that the merger with [ɸ] was a later areal change that spread across all extant dialects, possibly occurring simultaneous with or after the loss of the corresponding voiced fricatives), or to reconstruct Proto-Italic with the phonemes' voiceless allophones merged into /ɸ ~ β/, and their voiced allophones becoming independent phonemes /ð/, /ɣʷ/. Both of these sounds are relatively uncommon cross-linguistically, and eventually they were eliminated in all later languages, but differently in each.

Vowels

• /ə/ was perhaps not a true phoneme, but was inserted before consonants as a prop vowel. It can be reconstructed based on the outcome of the Proto-Indo-European syllabic nasals *m̥ and *n̥, which appear in Latin as *em, *en or *im, *in, but also as *am, *an in Osco-Umbrian alongside *em, *en. Thus, it appears necessary to reconstruct /ə/ as a distinct sound. However, Meiser reconstructs a nasal vowel /ẽ/ as this prop vowel, citing how Old French /ẽ/ evolved to modern French /ɑ̃/ as a parallel.^[12]

Proto-Italic had the following diphthongs:^[11]

• Short: *ai, *ei, *oi, *au, *ou
• Long: *āi, *ēi, *ōi

Osthoff's law remained productive in Proto-Italic. This caused long vowels to shorten when they were followed by a sonorant and another consonant in the same syllable: VːRC > VRC. As the long diphthongs were also VːR sequences, they could only occur word-finally, and were shortened elsewhere. Long vowels were also shortened before word-final *-m. This is the cause of the many occurrences of short *-a- in, for example, the endings of the ā-stems or of ā-verbs.

Prosody

Proto-Italic words may have had a fixed stress on the first syllable, a stress pattern which probably existed in most descendants in at least some periods. In Latin, initial stress is posited for the Old Latin period, after which it gave way to the "Classical" stress pattern. However, fixed initial stress may alternatively be an areal feature postdating Proto-Italic, since the vowel reductions which it is posited to explain are not found before the mid-first millennium BC.^[13]

Furthermore, the persistence of Proto-Indo-European mobile accent is required in early Proto-Italic for Brent Vine's (2006) reformulation of Thurneysen-Havet's law (where pre-tonic *ou > *au) to work.^[14]

Nouns

Nouns could have one of three genders: masculine, feminine and neuter. They declined for seven of the eight Proto-Indo-European cases: nominative, vocative, accusative, genitive, dative, ablative and locative. The instrumental case had been lost. Nouns also declined for number in singular and plural. The dual number was no longer distinguished, although a few remnants (like Latin duo, ambō) still preserved some form of the inherited dual inflection.

Adjectives

Adjectives inflected much the same as nouns. Unlike nouns, adjectives did not have inherent genders. Instead, they inflected for all three genders, taking on the same gender-form as the noun they referred to.

Adjectives followed the same inflectional classes of nouns. The largest were the o/ā-stem adjectives (which inflected as o-stems in the masculine and neuter, and as ā-stems in the feminine), and the i-stems. Present active participles of verbs (in *-nts) and the comparative forms of adjectives (in *-jōs) inflected as consonant stems. There were also u-stem adjectives originally, but they had been converted to i-stems by adding i-stem endings onto the existing u-stem, thus giving the nominative singular *-wis.

Pronouns

Declension of Personal Pronouns:^[36]

Note: For the third person pronoun, Proto-Italic *is would have been used.

Declension of Relative Pronouns:^[37]

Declension of Interrogative Pronouns:^[37]

Declension of Demonstrative Pronouns:^[38]

*is "this, that"

Verbs

Present Aspect^[39]

From Proto-Indo-European, the Proto-Italic present aspect changed in a couple of ways. Firstly, a new past indicative suffix of *-β- was created. This likely occurred due to the elision of word-final *i within the Indo-European primary verb endings (E.g. PIE Present Indicative *h₁ésti > PIt *est, but also PIE Past Indicative *h₁ést). Secondly, the desiderative suffix of *-s-/-so- became the future suffix in Proto-Italic. The subjunctive of this desiderative-future, with a suffix of both -s- and a lengthening of the following vowel, was used to represent a potentialis and irrealis mood. Finally, while the subjunctive and the optative of PIE were still in principle different moods, the moods became merged in Post-PIt developments (E.g. PIt subjunctive *esed vs optative *siēd which became Latin present subjunctive sit); this can be already seen in the Proto-Italic phase, where the subjunctive mood began to take secondary endings as opposed to the primary endings they exhibited in PIE (c.f. the Sabellian reflex of the PIt 3rd person singular imperfect subjunctive being -d and not *-t).

The PIE dual person was also lost within PIt verbs just as it was in PIt nouns.

First Conjugation

This Conjugation pattern was derived from the PIE suffix *-eh₂-yé-ti, and formed primarily denominative verbs (I.e. deriving from a noun or an adjective).

Example Conjugation: *dōnā- (to give)^[40]

Second Conjugation Causative

This conjugation pattern was derived from PIE *-éyeti, and formed causative verbs (I.e. expressing a cause) from "basic" 3rd conjugation verbs.

Example Conjugation: *mone- (to warn)^[41]

Second Conjugation Stative

This conjugation pattern was derived from PIE *-éh₁ti (or the extended form *-eh₁yéti), and formed stative verbs (I.e. indicating a state of being).

Example Conjugation: *walē- (to be strong)^[42]

Third Conjugation

The bulk of Proto-Italic verbs were third-conjugation verbs, which were derived from Proto-Indo-European root thematic verbs. However, some are derived from other PIE verb classes, such as *linkʷō (PIE nasal-infix verbs) and *dikskō (PIE *sḱe-suffix verbs).

Example Conjugation: *ed-e/o- (to eat)^[43]

Third Conjugation jō-variant

This conjugation was derived from PIE *ye-suffix verbs, and went on to form most of Latin 3rd conjugation io-variant verbs as well as some 4th conjugation verbs.

Example Conjugation: *gʷen-je/jo- (to come)^[44]

Athematic Verbs

Only a handful of verbs remained within this conjugation paradigm, derived from the original PIE Root Athematic verbs.

Example Conjugation: *ezom (copula, to be)^[45][39]

In addition to these conjugations, Proto-Italic also has some deponent verbs, such as *ōdai (Perfect-Present), as well as *gnāskōr (Passive-Active).

Perfective Aspect^[39]

According to Rix(2002), if a verb stem is present in both the Latino-Faliscan and Osco-Umbrian (Sabellian) branches, the present stem is identical in 90% of cases, but the perfect in only 50% of cases. This is likely because the original PIE aorist merged with the perfective aspect after the Proto-Italic period. Thus, the discrepancy in the similarities of present versus perfect stems in the two groupings of the Italic clade is likely attributed to different preservations in each group. The new common perfect stem in Latino-Faliscan derives mostly from the PIE Perfective, while the perfect stem in Osco-Umbrian derives mostly from the PIE aorist.

In the Proto-Italic period, the root perfect of PIE was no longer productive. However, other PIE perfect and aorist stems continued to be productive, such as the reduplicated perfect and lengthened-vowel perfect stems, as well as the sigmatic aorist stem (found in Latin dīcō, dīxī).

Sometimes, multiple perfect forms for each stem. For example, De Vaan gives the forms *fēk-, *fak- for the perfect stem of *fakiō, and the reduplicated form <FHEFHAKED> is also attested on the Praeneste fibula in Old Latin.

In addition, there were some new innovations within the perfective aspect, with the -v- perfect (in Latin amō, amāvī) and the -u- perfect (moneō, monuī) being later innovations, for example.

Example Long-Vowel Conjugation: *fēk- (to have done).^[46] Alternatively *θēk- (from PIE *dʰeh₁-) if PIt is reconstructed at a stage before /xʷ/ and /θ/ had merged with /f/ [ɸ].

Example Reduplicated Conjugation: *fefu- (to have been)^[45]