n (1) 焦点(point in a system of lenses or another optical system at which rays of light come together or from which they appear to spread) [C]：principal/real/virtual～(物)主/实/虚焦点;bring sth/come into～焦点对准;清晰;(be/go) out of～焦点没对准;模糊;

(2) 焦距(point of distance at which an object is clearly seen by the eye through lens) [U]：take out the binoculars and adjust the～拿出望远镜调节焦距;the right～for getting a distinct image 能看清远处景象的正确焦距;

(3) 调(聚)焦(器) (adjustment of an optical device necessary to produce a clear image) [C]：the～on the camera/the telescope 照相机/望远镜上的调焦器;

(4) 兴趣，(注意，活动的)中心(center of interest，attention or activity)[C，通常sing]：want to be the～of everyone's attention 想成为每个人注意的中心;(café) be the～of social life in many French towns (咖啡馆)是法国许多城市社交生活的中心;(changes in the urban environment) be the～of public interest (城市环境的变化)是公众关心的中心问题;〖同〗center，middle，heart，core;

v (1) 调(聚)焦(adjust the distance to get a clear picture) [T+n，T+n+prep(on)]：Remember to～the camera/the picture before taking the photograph. 记住在拍照片之前，先调好相机的焦距/图像的距离。A camera lens～es light on the film. 相机的透镜把光线聚集在胶片上。～the telescope on that distant lighthouse/the aircraft 把望远镜对准远处的灯塔/飞机;〖同〗center，fix;

(2) 1) 专心于(concentrate on) [I，I+prep(on)]：I'm so tired that I'm not～ing very well. 我太累了，无法集中注意力。Public attention～ed on the election/the Olympics/the problem of industrial relations. 公众的注意力集中在选举/奥运会/劳资关系问题上。2) 把(精神、注意力)集中于(direct (one's attention，etc) to) [T+n，T+n+prep (on)]：～one's thoughts 集中思想;～one's mind on work/the main problem 将心思集中在工作/主要问题上;～one's attention on the injustice of the situation/the meaning of each sentence 把注意力集中在不公平的情况/每个句子的意思上;

【辨异】 focus与concentrate的区别见CONCENTRATE。