mrkgnao: Both are right and both can be found on both sides of the Atlantic, but flat is more common in UK and apartment more common in US.
Carradice: Sure! I mean, both of you, Lexor and mrkgnao being right, with the connotation of appartments being somewhat smaller and condos larger, and 'flat' being neutral about size when used in the UK (
condo being uncommon to the East of the Atlantic). Just being curious, is all.
I didn't realise you were referring to Lexor's answer. I'm not aware of a consistent difference in size between flats and apartments where both are used. Except, of course, that flat is four letters and apartment nine.