Portuguese allows nasal diphthongs, which contrast with their oral counterparts, like the pair mau /ˈmaw/ "bad" and mão /ˈmɐ̃w̃/ "hand".
Likewise, pronunciation keys in English dictionaries do not always indicate nasalization of French or Portuguese loanwords.
Rodney Sampson described a three-stage historical account, explaining the origin of nasal vowels in modern French.
Languages written with Latin script may indicate nasal vowels by a trailing silent n or m, as is the case in French, Portuguese, Lombard (central classic orthography), Bamana, Breton, and Yoruba.
The same practice can be found in Portuguese marking with a tilde in diphthongs (e.g. põe) and for words ending in /ɐ̃/ (e.g. manhã, irmã).
While the tilde is also used for this purpose in Paraguayan Guaraní, phonemic nasality is indicated by a diaeresis ( ¨ ) in the standardized orthographies of most varieties of Tupí-Guaraní spoken in Bolivia.
Nasalization in Arabic-based scripts of languages such as Urdu, as well as Punjabi and Saraiki, commonly spoken in Pakistan, and by extension India, is indicated by employing the nasal vowel, a dotless form of the Arabic letter nūn (ن) or the letter marked with the maghnūna diacritic: respectively ں, always occurring word finally, or ن٘ in the medial form, called "nūn ghunna".
There is no orthographic way to denote the nasalization, but it is systematically taught as part of the essential rules of tajwid, used to read the Qur'an.