An act or the fact or manner of falling upon or affecting; occurrence.

(事件的)发生；影响。

Range or degree of occurrence.

发生率；影响程度。

Position of two figures in relation to each other when they partly coincide.

【数】(几何)(图形)接合。

The falling of a line, or a ray of light on a surface.

【理】入射(角)；投射(角)。