1 [sing] (formal 正式)an incidence of sth the number of times sth (usually sth unpleasant) happens; the rate of sth 发生率（一般指不好的事情）: a high incidence of crime/disease/unemployment 高犯罪率╱发病率╱失业率

2 [U] (technical术语) the way in which a ray of light meets a surface （光线的）射入: the angle of incidence 入射角 ➔incident adj the incident ray (= the one that meets a surface) 入射线the incident angle (= at which a ray of light meets a surface) 入射角 ☞picture at reflection 见reflection插图