Nasalisation is the addition of nasal resonance to a sound, typically a vowel, caused by the lowering of the velum (soft palate), allowing air to pass through the nasal cavity simultaneously with the oral cavity. In English, nasalisation is allophonic; in some other languages, it is phonemic.
In English, vowels adjacent to Nasal consonants (/m n ŋ/) acquire nasal quality through Coarticulation. The velum lowers for the nasal consonant, and this lowering extends into the neighbouring vowel:
This nasalisation is allophonic: it is an automatic, predictable phonetic process that speakers produce and listeners hear without conscious awareness. It never changes word meaning: [æ] and [æ̃] are Allophones of the same Phoneme /æ/.
In several languages, nasalisation is phonemic: it distinguishes word meanings:
| Language | Oral | Nasal | Meaning difference |
|---|---|---|---|
| French | beau /bo/ (beautiful) | bon /bɔ̃/ (good) | Phonemic contrast |
| Portuguese | lá /la/ (there) | lã /lɐ̃/ (wool) | Phonemic contrast |
| Hindi | ā /aː/ | ā̃ /ãː/ | Phonemic contrast |
| Vietnamese | Various oral vowels | Corresponding nasal vowels | Phonemic contrast |
Vietnamese learners of English have phonemic nasalisation in their L1. This can lead to:
French and Portuguese learners may transfer phonemic nasal vowels into English, producing vowels with stronger nasalisation than English norms.
For most learners, English nasalisation does not need explicit teaching because it occurs naturally through Coarticulation. However, teachers should be aware of it when diagnosing accent features and when working with learners whose L1 makes phonemic use of the distinction.
Nasalised vowels are marked with a tilde diacritic: [ã], [ẽ], [ɔ̃]. In English phonemic transcription, nasalisation is not marked because it is predictable from context.