An obstruent (/ˈɒbstruːənt/ OB-stroo-ənt) is a speech sound such as [k], [d͡ʒ], or [f] that is formed by obstructing airflow. Obstruents contrast with sonorants, which have no such obstruction and so resonate.[1] All obstruents are consonants, but sonorants include vowels as well as consonants.