used to draw attention to a fact that is not obvious or has not previously been mentioned :
It was a difficult situation, when you think about it.
used to draw attention to a fact that is not obvious or has not previously been mentioned :
It was a difficult situation, when you think about it.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005