形容词

1. 焦点的;有焦点的
Focal is used to describe something that relates to the point where a number of rays or lines meet.

2. 重要的;中心的
Focal is used to describe something that is very important.

1. having or localized centrally at a focus

e.g. focal point
focal infection

2. of or relating to a focus

e.g. focal length