Moderator note: This thread is split from here, because this is a different topic. I'd be inclined to say 어머님 was more respectful/deferential than 어머니, rather than more polite. That distinction matters for learners rather a lot. One of the things that most perplexes foreigners about the Korean honorific system, and one that many Koreans find hard to explain because they've never really needed to think about it in the abstract, is that there are two distinct axes involved: an axis of deference; and an axis of courtesy. These axes are related, but nevertheless distinct. When speaking or writing Korean you can(and indeed should) be courteous to everyone you speak to or about (except very close friends, very small children and animals) no matter what their status relative to yourself. But you can and always must be deferential to your elders and betters and "humble" in reference to yourself, no matter what your age or standing in life is. These two axes co-exist and interact. You can't be correctly deferential without also being courteous; and showing the correct degree of deference and "humility" (I use scare quotes because I'm talking here about codified linguistic choices rather than inner attitudes) is in turn a pre-requisite of true courtesy. Most learners are aware that they risk offending Koreans by "talking down" to them inappropriately; they tend to be less aware that it can also be discourteous to "talk up" to people in circumstances where a more relaxed form of address would sound less stand-offish and avoid creating the impression that you felt the person you were "talking up" to was excessively self-important. One of the methods Koreans use to deflate people they think are being pompous is by addressing them in an over-the-top (mock) deferential way. So I wouldn't like the original poster to go away with the idea that referring to a friend's mother in more or less casual conversation with no-one else present simply as 네 어머니 is in any sense discourteous (though you would never ever address the lady in question as 어머니 to her face or refer to her than way when talking about her to any third party other than your friend in private.) But yes, adding the honorific affix ~님 (a particle which is on the axis of deference rather than that of courtesy) is indeed more respectful, and respect for any elder whatsoever is always a good thing to show in Korean culture.