[UK and ANZ] usually -ise [verb] - to understand (a situation), sometimes suddenlyThey didn't realize the danger they were in. [T]"Do you realize (that) this is the third time you've forgotten?" she said angrily. [+ (that) clause]I realize how difficult it's going to be, but we must try. [+ wh- word]I didn't fully realize what an enthusiastic father Nigel would be. [+ wh- word]As he watched the TV play, he suddenly realized (that) he'd seen it before. [+ (that) clause]"You're standing on my foot." "Sorry, I didn't realize." [I]See also realize at real (NOT IMAGINARY).
Meaning of REALIZE in English
Cambridge English vocab. Кембриджский английский словарь. 2012