Metaphony (Romance languages)

In the Romance languages, metaphony was an early vowel mutation process that operated in all Romance languages to varying degrees, raising (or sometimes diphthongizing) certain stressed vowels in words with a final or  or a directly following. This is conceptually similar to the umlaut process characteristic of the Germanic languages. Metaphony is most extensive in the Italo-Romance languages, and applies to nearly all languages of Italy. However, it is absent from Tuscan, and hence from Standard Italian.

Italo-Romance languages
Metaphony in central and southern Italo-Romance (i.e. excluding Tuscan) affects stressed mid-vowels if the following syllable contains or. As a general rule, the high-mids are raised to, and the low-mids  are raised to  or diphthongized to. Metaphony is not triggered by final. The main occurrences of final are as follows:
 * The plural of nouns in -o (< nominative plural -ī).
 * The plural of nouns in -e (either a regular development of alternative third-declension accusative plural -īs, or analogical to plural -ī).
 * The second-person singular present tense (a regular development of -īs in verbs in -īre and analogical in verbs in -ere, -ēre, -āre; in Old Italian, the ending -e is still found in -are'' verbs).
 * The first-person singular past indicative (< -ī).

The main occurrences of final are as follows: The main occurrence of final is in masculine "count" nouns (< -um).
 * The first-person singular present indicative (< -ō).
 * Masculine "mass" nouns, and "neuter" (mass-noun) demonstratives (disputed origin).

Metaphony in the northern Italian languages (those to the north of Tuscany) is triggered only by final. In these languages, as in Tuscan, final was lowered to ; it evidently happened prior to the action of metaphony. In these languages, metaphony also tends to apply to final, raising it to or.

In most Italian languages, most final vowels have become obscured (in the south) or lost (in the north), and the effects of metaphony are often the only markers of masculine vs. feminine and singular vs. plural.

Western Romance languages
In all of the Western Romance languages, metaphony was triggered by a final (especially of the first-person singular of the preterite), raising mid-high stressed vowels to high vowels. (It does not normally occur in the nominative plural noun forms in Old French and Old Occitan that have a reflex of nominative plural, suggesting that these developments were removed early by analogy.) Examples:
 * vīgintī "twenty" > *vigintī > PIR > Italian venti; but > pre-PWR  > PWR  > Old Spanish veínte (> modern veinte ), Old Portuguese veínte (> viínte > modern vinte), Old French vint (> modern vingt ).
 * fēcī, fēcit "I did, he did" (preterite) > Italian feci, fece; but > pre-PWR >  > PWR  > Old Spanish fize, fezo (> fize, fizo > modern hice, hizo), Portuguese fiz, fez, Old French fis, fist (< *fis, feist).

Astur-Leonese
In some of the Astur-Leonese dialects, in northern Spain, a distinction between mass and count nouns appeared at an early stage. Count nouns from Latin masculines preserved the -u (<um) from Latin accusative, while mass nouns from Latin masculines (traditionally called "mass-neuter") were marked by -o. In addition, Astur-Leonese marked masculine plurals with (< -ōs).

In this situation, only masculine singular count nouns developed metaphony, as they were the ones marked with a, and mass nouns and plurals, marked with , did not. This ending system has been preserved in only central Asturian dialects. Unlike metaphony, which is considered dialectal, it has also been included in the standard version of Asturian.

However, at later stages, Eastern Astur-Leonese dialects (Eastern Asturias and Cantabria) lost the u/o distinction in noun gender markers. Some of those dialects also lost metaphony and the noun count/mass distinction altogether, keeping it only in their pronoun systems, others, such as Pasiegu from Eastern Cantabria closed all their mid-vowels in word ending syllables, and relied on metaphony as a means for distinguishing mass/count nouns.

Some Astur-Leonese dialects also presented i-triggered metaphony. It is also considered dialectal, and it is most prevalent in imperatives (durmi < PIR dormi, sleep!), preterites (vini < PIE veni, I came) and demonstratives (isti < esti, this; isi < esi, that). Sometimes it prevents diphthongization (durmi vs duermi, sleep!; curri vs cuerri, run!) by closing the mid vowel in the verbal stem.

Portuguese
Raising of to  by a following final  occurs sporadically in Portuguese. Example: porcum, porcōs "pig, pigs" > Proto-Ibero-Romance > Portuguese porco  vs. porcos ; novum, novōs, novam, novās "new (masc., masc. pl., fem., fem. pl.)" > PIR  > Portuguese novo  vs. novos, nova, novas. In this case, Old Portuguese apparently had in the singular vs. in the plural, despite the spelling ⟨-o -os⟩; a later development has raised plural to. Furthermore, the mass/count distinction is expressed very differently: Only a few "mass neuter" demonstratives exist, and they have a higher rather than lower vowel (tudo "everything" vs. todo "all (masc.)", isto "this (neut.)" vs. este "this (masc.)"). In addition, the original pattern has been extended to some nouns originally in.

Metephony on present tense and imperative verbs also occurs.

Romanian
Romanian shows metaphony of the opposite sort, where final (and also, especially in the case of ) caused a diphthongization  > ,  > ,  > : cēram "wax" > ceară; equam "mare" >  >  > iapă; flōrem "flower" > floare; nostrum, nostrī, nostram, nostrās "our (masc. sg., masc. pl., fem. sg., fem. pl.)" >  > nostru, noștri, noastră, noastre.

Sardinian
Sardinian likewise has a distinction between final and  (again with plural ), along with metaphony. In the conservative Logudorese and Nuorese dialects, the result of metaphony is a non-phonemic alternation between (when final  or  occurs) and  (with other final vowels). In Campidanese, final have been raised to, with the result that the metaphonic alternations have been phonemicized.