继母和后妈翻译成英文都是step mother。但汉语里面继母和后妈表意不同。继母是中性词汇，还可以作为尊称，比较文雅，多用作书面语和正式场合；后妈比较口语化且稍带贬义。例如有人说：某某是她的继母。你不但可以从中知道两人的关系，而且可以大概判断出两人关系相对比较融洽。如果说成某某是她的后妈，就多少可以判断出说话人对她的继母有点意见。所以两个词在汉语中指代一致却表意不同。

as someone answered, 继父与继母，后爸与后妈，in some place of china, people also called step-father and step-mother 晚爹与晚娘

nono，继父should be together with 继母。后爸 is coupled with 后妈。you just took it from two different type. the other parts exist.

It's like 父母and 爸妈。the first one is more official or for writing，more formal.the second one is more used for speaking. So u can say 继父、继母，or后爸、后妈，they are the same.

标准的说法就是继母，后妈有点地方口语。