1.

抓牢

The girl kept catching on to her mother's skirt.

小女孩一直紧紧地拉着妈妈的裙子。

2.

理解

I don't quite catch on to what she is saying.

我不太明白她在说些什么。

3.

流行

It is a nice song and I think it will catch on quickly.

这首歌很好,我想它会很快流行起来。