are you the secretary?

[Sabine Dippel]

Okay, so I finally ask. What does Ms. mean? I gathered as much that it is 
supposed to finish with the difference between Miss and Mrs., but what 
word does this abbreviation stand for? 
I have been wondering about this for a long time, but now that it turns
up so often in this thread, I finally want to know.

Sabine
(a person who speaks English well enough, but has never lived in an 
English-speaking country).