1.focus用作名词时原始意义是“火炉”,引申为“焦点”,转化为动词则为“(使)聚焦”,“(使)集中”。即“调整…的焦点或焦距以便看清”,引申则表示“使(注意力等)集中于某物”。
2.focus用作及物动词时,可以接望远镜、焦点等作宾语,也可以接阳光等作宾语,还可以接目光等作宾语。focus用于比喻作“致力于”解时,则可以接mind, attention等作宾语。
3.focus也用作不及物动词,这时常和介词on连用,表示“聚焦于…”“致力于…”等。

focus on (v.+prep.)
1.使聚焦于; 使直射于 aim sth directly onto sth
▲focus on sth
A near-sighted person cannot focus accurately on distant objects.一个近视的人不能够准确地调节眼睛以看到远处物体。
▲focus sth on sth
He focused the sun's rays on a paper with a burning-glass.他用一面凸透镜把阳光聚焦在纸上。
If you focus bright sunlight on dry wood with a glass, it will start burning.假如你用镜子将强烈的阳光聚焦于干燥的木头上,它便会燃烧起来。
2. 对(某事或做某事)予以注意 pay attention to sth or to do sth
▲focus on sth/v-ing
Today we're going to focus on the question of homeless people.今天,我们主要讨论无家可归者的问题。
Many firms are focusing on increasing their markets overseas. 许多商行都在注意在国外扩大市场。
3.致力于 pay attention to
▲focus sth on sb/sth
He focused his mind on his lessons.他把心思集中在功课上。
You should focus your attention on your work.你应该聚精会神地工作。
We must focus our attention on the question of reducing costs. 我们必须将注意力集中在降低费用的问题上。
◇ 用于be ～ed结构
When the coin failed to appear, attention was focused once more on poor Lebeau. 当找不到那枚古币以后,大家的注意力再次转到勒保身上。
All eyes were focused on him when he came in.他进来时大家都注视着他。
4.把…作为兴趣中心 like sth most
▲ focus on sth/v-ing
Today, we're going to focus on the relationship between freedom and necessity.今天,我们将集中讨论自由和必然之间的关系这一问题。
This year our meeting focuses on the question of children's rights.今年我们会议的中心问题是儿童权益问题。
The show focuses on making fun of politicians.这场演出旨在嘲弄那些政客。

用作不及物动词
▲S+～(+A)
A defect of vision prevented him from focusing accurately.视力缺陷使他无法准确聚焦。
He must be very tired today, he doesn't seem to focus at all.他今天一定很累,他似乎无法专心思考。
用作及物动词
▲S+～+n./pron.
He focuses the lens of a microscope.他调整显微镜的镜片以定焦点。
His eyes were so tired that he had difficulty focusing it.他的眼睛累了,无法准确聚焦。
◇ 用于be ～ed结构
Unless the object is properly focused the photograph will be blurred.除非把焦距调准,否则拍出的照片是不清楚的。

focus, centre, centralize, concentrate
参见centre条。

The camera has two focuses.这部相机有两个焦距。
She was the focus of everyone's attention.她是大家注意的焦点。
He is adjusting the focus of camera.他正在调相机的焦距。
The coffee shop is the focus of social life in French.在法国,咖啡馆是社交生活的中心。

［同义词］ v. concentrate n. center, middle
［词源］＜拉丁语focus(火炉)