cut down是减少、削减的意思，表示直接把后面sth去掉或砍掉。

如：cut down production 减少产量

cut down on 表示“减少……的量”，表示把sth 的量减少一部分。

如：The doctors have told me to cut down on smoking. 扩展资料

You need to cut down on starches.

你有必要少吃些含淀粉的东西。

I won't have a cigarette, thanks ─ I'm trying to cut down.

谢谢，我不抽。我现在尽量少抽烟。

Most schools are extremely unwilling to cut down on staff in order to cut costs.

大部分学校都很不愿意为减少开支而裁员。