What is a fricative in phonetics?

A fricative is a type of consonant sound that is produced by forcing air through a narrow channel, which creates turbulence and friction as the airflow is partially obstructed. This is characteristic of fricatives, as the airflow does not stop completely, but instead, the constriction allows for a continuous flow of air that results in a hissing or buzzing sound.

For example, sounds like /f/, /v/, /s/, /z/, /ʃ/ (as in "sh"), and /ʒ/ (as in "measure") are all classified as fricatives because of the way they are articulated in the vocal tract. The constriction can occur at various places, such as between the bottom lip and the upper teeth, or between the tongue and the alveolar ridge.

Other options presented do not correctly define fricatives; one describes a voiced sound (which applies to voiced fricatives but not exclusively to them), another describes how stops are produced (which completely block airflow), and the last refers to rounded lip sound production, which is not specifically related to how fricatives are classified. Therefore, the correct choice effectively captures the nature of how fricatives are articulated.