Split describes the act of dividing one physical object into two (or more) objects. The common synonyms (同义词) for split are tear, break, chop (砍) etc. It emphasizes the same thing is divided.

It also implies force (强制力) is used to separate something that was one thing.

Split强调的是使用力量将一个物体切成两块或多块。强调的是原本一体的东西​被分割成了多块。

For example, I split wood with an axe (斧).

Separate is to take two or more things that were already different and move them away from each other. The common synonyms for separate are detach (分离), disconnect.

Separate强调的是分开本来就不是一个整体的混合体。混合体的个体都是独立个体，相互间不存在​依附关系。

For instance, The teacher separates the boys and the girls.

Divide simply means to make or keep separated. It is the most abstract (抽象的) of the terms. Things that are divided may not have been one unit and may not need to be cut with anything. It can be used for things like groups of people, etc.

Divide是最抽象的表达​。强调的是逻辑、概念、关系的分开​。被分开的个体可能本来就不是一体的。

For instance, you have to divide your time between work, entertainment (娱乐) and family duties.

Slice means smoothly cut something into thin strips with a knife or blade (刀片). It implies the pieces have precise shape, so it is most commonly associated with food.

Slice强调的是用刀片将某个物体切割成某种特定的形状​，因此常常用于食物、工业行业相关的切割。Split没有这层​意思。

For instance, please slice these tomatoes for me, i will cook them later.

英语单词split, separate, divide, slice的区别