How are fricative consonants such as /s/, /f/, and “th” formed?

Fricative consonants, such as /s/, /f/, and "th," are produced by bringing two articulators in the mouth into close approximation to partially obstruct the airstream. This partial closure forces air through a narrow passage, creating turbulent airflow that generates audible friction, similar to the sound of wind whistling around a corner.12

The specific formation depends on the articulators involved:
* Mechanism: The mouth is positioned to block the passage of air without making a complete closure, allowing air to escape through a constriction.1
* Classification: Fricatives are often categorized by the shape of the constriction (such as slit or grooved) or by acoustic criteria, such as sibilants (like /s/), which involve the tongue tip or blade being brought near the roof of the mouth to create a hissing sound.23
* Variations: Depending on the placement of the articulators, these sounds can be bilabial, labiodental, dental, alveolar, palatal, velar, or uvular. For example, /f/ is typically labiodental, while the "th" sounds are dental.1