Separate 既可以表示夫妻“法律上离婚”，也可以表示“分居”，例如：
She was separated from her husband last year.
去年她和丈夫离婚了
The child's parents have separated.
这孩子的父母已经分居了。
那离婚后“再婚”要怎么说呢？就是remarry，例如：
Research suggests that the best time to remarry is before a child's 10th birthday or after his/her 16th. 研究建议最佳的再婚时间是在孩子10岁之前或是16岁之后。
She remarried her former husband ten year after their divorce.
她与原来的丈夫离婚十年后又复婚了