quality:corruption
Nasalization

In both French and Portuguese, nasal vowels eventually developed from sequences of a vowel followed by a nasal consonant (/m/ or /n/). Originally, all vowels in both languages were nasalized before any nasal consonants, and nasal consonants not immediately followed by a vowel were eventually dropped. In French, nasal vowels before remaining nasal consonants were subsequently denasalized, but not before causing the vowels to lower somewhat, e.g. dōnat "he gives" > OF dune /dunə/ > donne /dɔn/, fēminam > femme /fam/. Other vowels remained nasalized, and were dramatically lowered: fīnem "end" > fin /fɛ̃/ (often pronounced); linguam "tongue" > langue /lɑ̃ɡ/; ūnum "one" > un /œ̃/, /ɛ̃/.

In Portuguese, /n/ between vowels was dropped, and the resulting hiatus eliminated through vowel contraction of various sorts, often producing diphthongs: manum, *manōs > PWR * manu, ˈmanos "hand(s)" > mão, mãos /mɐ̃w̃, mɐ̃w̃s/; canem, canēs "dog(s)" > PWR * kane, ˈkanes > * can, ˈcanes > cão, cães /kɐ̃w̃, kɐ̃j̃s/; ratiōnem, ratiōnēs "reason(s)" > PWR * raˈdʲzʲone, raˈdʲzʲones > * raˈdzon, raˈdzones > razão, razões /χaˈzɐ̃w̃, χaˈzõj̃s/ (Brazil), /ʁaˈzɐ̃ũ, ʁɐˈzõj̃ʃ/ (Portugal). Sometimes the nasalization was eliminated: lūna "moon" > Galician-Portuguese lũa > lua; vēna "vein" > Galician-Portuguese vẽa > veia. Nasal vowels that remained actually tend to be raised (rather than lowered, as in French): fīnem "end" > fim /fĩ/; centum "hundred" > PWR tʲsʲɛnto > cento /ˈsẽtu/; pontem "bridge" > PWR pɔnte > ponte /ˈpõtʃi/ (Brazil), /ˈpõtɨ/ (Portugal).

Romanian shows evidence of past nasalization phenomena, the loss of palatal nasal in vie < Lat. vinia, and the rhotacism of intervocalic /n/ in words like mărunt < Lat. minutu for example. The effect of nasalization is observed in vowel closing to /i ɨ u/ before single /n/ and nasal+consonant clusters. Latin /nn/ and /m/ did not cause the same effect.