a situation in which two or more people or things are separated

During the war many couples had to endure long periods of separation (= not being together). 战争期间，很多夫妇不得不忍受长期分离之苦。

After many years the South African government finally abandoned its apartheid system of racial separation. 多年之后，南非政府最终废除了种族隔离制。

an arrangement, often legal, by which two married people stop living together as a couple

Couples may agree to divorce each other after a separation. 分居之后，夫妻双方可以协议离婚。

They're considering separation as an option. 他们正在考虑选择分居。