In phonetics, an obstruent (/ˈɒb.stru.ənt/, OB-stroo-ənt) is a speech sound that is formed by obstructing airflow, such as [d] (plosives/oral stops), [ʒ] (fricatives), or [d͡ʒ] (affricates). Obstruents contrast with sonorants (also known as resonants), which have no such obstruction and therefore are "sonorous" and "resonate". All obstruents are consonants, but sonorants include vowels as well as consonants. As a distinctive feature, obstruents are denoted as [−son].
Compare occlusives, a class of speech sounds which includes both oral and nasal stops as well as affricates, but excludes fricatives, and contrasts with continuants.
Obstruents are subdivided into:
Obstruents are often prototypically voiceless, but voiced obstruents are common. This contrasts with sonorants, which are prototypically voiced and only rarely phonemically voiceless.