realize vs recognize

I know an American who is teaching in Tokyo. He believes that he is one of the best ESL teachers. But, I heard that when one of his students asked him about the difference between to "realize" and to "recognize," he said "English is sometimes very difficult."

A dictionary explains this way:

realize: to understand a situation, sometimes suddenly

recognize: to accept that something is legal, true, or important.

Cambridge Advanced Learner's Dictionary