A type of consonant in which the air escapes through a narrow gap created between lips, teeth and tongue, as in English /f/ fine sign, vine, etc.

Phonemes made by forcing air through a very small opening, e.g., between the top teeth and the tongue or lip; also called "hissing" or "hisser sounds." Examples: |f|, |th| as in thumb, |s|, |sh|, |v|, |TH| as in this, |z|, |zh| as in measure. (|h| is sometimes considered to be in this category.)

Airflow noise resulting from obstructions - but not complete blockage - of the vocal tract. For example, the tongue and teeth obstruct airflow when producing the sounds "s," "z," and "th."