0_Apprentice
Ever have an Ex you can't get out of your mind (for whatever reason)?
1_Wizard
that depends, as a prefix ex can refer to a variety of relationships. 
0_Apprentice
True enough, let's say an EX, well not lover, but someone who you causally dated
1_Wizard
I think most people understand that. As it is often used as a derogatory tinge. 
0_Apprentice
What do you mean 'derogatory tinge'?
1_Wizard
Well, its usually not positive. sometimes its assumed to be a former romantic partner or spouse. 