power brake: a brake on an automobile that magnifies a small force applied to the brake pedal into a proportionately larger force applied to slow or stop the vehicle
instrumentality: an artifact (or system of artifacts) that is instrumental in accomplishing some end
linguistic performance: (linguistics) a speaker's actual use of language in real situations; what the speaker actually says, including grammatical errors and other non-linguistic features such as hesitations and other disfluencies (contrasted with linguistic competence)