两者均可表示“分开”：divide 通常指把整体分为若干部分，其后常接介词 into;而 separate 通常指把原来连在一起或靠近的东西分隔开来，其后常接介词 from。如：

The world is divided into seven continents. 世界被分成七大洲。

Divide the money among the six of you. 这笔钱你们六个人分。

The food was divided amongst the poor. 食物都分给了穷人。

The children divided the money among (between) them. 孩子们在他们之间把钱分了。

The money was divided into two halves. 钱被分成了两半。

United we stand, divided we fall. 团结则存，分裂则亡。

Countable nouns may be sub-divided into two categories? 可数名词又可分为两类。

We’d better separate the good ones from the bad ones. 我们最好把好的和坏的分开。

She doesn’t want to be separated from him. 她不想和他分开。

The couple separated because they were not compatible. 这对夫妻因不合而分居。

The two parts of the pipe have separated at the joint. 这个管子从接口处分成两截了。

The branch has separated from the trunk of the tree. 这个树枝已从树干上脱落了。

This patient should be separated from the others. 这个病人应该隔离。

注：以上区分并不十分严格，有时两者可换用。如：

The field is divided [separated] into five parts. 这块田被分为 5 块。

The Red Sea separates [divides] Africa from Asia. 红海把非洲和亚洲分开。