protractor

n instrument, usu in the form of a semi-circle with degrees (0 to 180) marked on it, used for measuring and drawing angles 量角器; 分度规.

protector, protectorate, protege (fem 阴性作 protegee), protein, protein-rich, protest, Protestant, Protestantism, protestation, protester, protestingly, protocol, proton, protoplasm, prototype, protozoan, protozoon (also protozoan), protract, protracted, protraction, protrude, protrusion, protrusive, protuberance, protuberant, proud, proudly, Prov, provable, provably, prove, proven, provenance, provender, proverb, proverbial, proverbially, provide, provide for, provide somebody with,