Glottal stops

Nasalization

However, the phonetic status of truly "nasalized" glottal stops is debated, depending on one's definition of nasality; similarly, although they may be contrastive in their underlying forms, a perceptual difference in their surface realizations is doubted. Some linguists have argued that because nasal airflow and glottal closure are mutually exclusive features, phonetic nasalized glottal stops are impossible entities. Other linguists have argued that because the gestural lowering of the velum (opening of the velopharyngeal port) that is associated with nasality is entirely compatible with glottal closure, they are not only possible but expected in some environments, particularly those where nasal harmony is not blocked by the presence of a glottal stop (such as in Sundanese, Acehnese, and Warao). Thus, the recognition of nasalized glottal stops as a phonetic possibility is a matter of whether nasality is defined as the presence of nasal airflow or by the exhibition of a lowered velum.