Yes, students always address their professors by 교수님. 교생님 is a different word. 교생 refers to college students in the teaching discipline who come out to high schools on an internship-like program to gain real life teaching experience. The high school students may call them 교생님 as it is customary to call anyone senior to you using the suffix 님. And as you mentioned, 교 can sometimes sound like 규. There is no word like 엄마니 or 엄머님. 엄마 is essentially a baby word, like Ma, so it is never used with 님 just as you wouldn't use Mrs. or "Dear" Ma. The word you heard must be 어머니 which is a noun like "mother" as well as a more mature address word. When you're small you use 엄마, and as you grow older you're likely to switch to 어머니 at some point. 어머님 is an honorific version of 어머니 you can use for someone else's mother or your own mother-in-law. Similarly, for "father", there's 아빠, 아버지, and 아버님. About the other words: - 형, 형님 - fine. 형님 is more respectful and formal. - 누나, 누님 - 누나님 is never used. 누님 is the traditional mature version of 누나. - 언니 - 언니 is never called 언니님, except maybe as a joke. - 아저씨, 아줌마 - 아저씨님 and 아줌마님 exist but kind of rare. They are more natural without -님. - 아가씨 - almost never used with -님 since it refers to a female younger than you. - 왕 - 왕님 sounds childish. There are many better words and titles for 왕, like 임금님, 대왕폐하, 상감마마, etc.