Historically, an unmarried lady was addressed as "Miss." , on the other hand, alludes to a married lady. "Ms." is a little more difficult to employ because it is used by and for both unmarried and married women. When addressing an unmarried woman, simply write "Mrs." or "Miss." If she is your friend, acquaintance, or colleague, then use her full name instead. These are the most common addresses for a married woman or a single girl: Mrs. , Miss, Ms. , Mr. (Not usually used with females who are not married). If you make an appointment with a doctor's office and they ask you to tell them what title you go by, here are some examples of answers you can choose from: Dr. Mrs. Mr. It depends on your situation. If you are not married then you can go by either one. If you are married then you should always go by your husband's last name.