In materials science, friability (/ˌfraɪ.əˈbɪləti/ FRY-ə-BIL-ə-tee), the condition of being friable, describes the tendency of a solid substance to break into smaller pieces under stress or contact, especially by rubbing.
Tougher substances, such as concrete, may also be mechanically ground down and reduced to finely divided mineral dust.
Some substances, such as polyurethane foams, show an increase in friability with exposure to ultraviolet radiation, as in sunlight.
Friable is sometimes used metaphorically to describe "brittle" personalities who can be "rubbed" by seemingly-minor stimuli to produce extreme emotional responses.
This testing involves repeatedly dropping a sample of tablets over a fixed time, using a rotating wheel with a baffle.