For example, Rybarikova retiring against Azarenka means what?
Did she quit?
How often does a player "retire" and why do they retire?
Did she quit?

How often does a player "retire" and why do they retire?


They're either injured; losing and can't be assed to keep going; don't want to embarrass themselves by recording a loss; protecting themselves against potential injury; or have fixed a match. I think that about covers it 