Proto-Romance language

Proto-Romance is the comparatively reconstructed ancestor of the Romance languages. It is effectively Late Latin viewed retrospectively through its descendants.

Diphthong
appears to be the only phonemic diphthong that can be reconstructed.

Phonetics

 * Vowels were lengthened in stressed open syllables.
 * Stressed may have yielded incipient diphthongs like  in metaphonic conditions.
 * Metaphony, if it is to be projected to Proto-Romance, may have initially been limited to open syllables. That is, it would have targeted allophonically lengthened.

Constraints

 * did not occur in unstressed position.
 * did not occur in the second syllable of words with the structure ˌσσˈσσ.

Palatalized consonants

 * There is scholarly disagreement over whether palatalization was phonemic in Proto-Romance.
 * Palatalized consonants tended to geminate between vowels. The extent of this varied by consonant. 
 * would have been an affricate like or.

Phonetics

 * in word-initial position was assigned a prop-vowel [ɪ], as in . 
 * was likely at first, with later developments varying by region. 
 * might have been fricatives or approximants between vowels.
 * might have been retroflex. 
 * might have been bilabial.

Constraints

 * did not occur in intervocalic position.

Morphology
The forms below are spelt as they are in the cited sources, either in Latin style or in phonetic notation. The latter may not always agree with the phonology given above.

Nouns
Nouns are reconstructed as having three cases: a nominative, an accusative, and a genitive-dative:  Some nouns of the –C type had inflections with alternating stress or syllable count: There were also ‘neuter’ nouns. In the singular they would have been treated as masculine and in the plural as feminine, often with a collective sense.

Comparative
For the most part, the typical way to form a comparative would have been to add magis or plus (‘more’) to a positive adjective. A few words were inherited with a comparative suffix -ior. Their inflections can be reconstructed as follows: 

Superlative
Superlatives would have been formed by adding definite articles to comparatives.

Tonic
The stressed or 'strong' forms:

Atonic
The unstressed or 'weak' forms:

Interrogative/relative
As follows: