I always get confused at the usage of these 2 words:
what’s the difference between them?
" How will I recognise you?"
“You will easily recognise my car, as it has no doors.”
" I recognised you at once."
" Do you realise what you have just said?"
" You must realise that not everyone thinks you are great."
" I now realise my mistake."
‘Recognise’ means know by looking at someone/something. You can use this as: I recognised you in the school photograph because you haven’t changed a bit in 20 years. ‘Realise’ means understand after consideration as in: I realise now that I made a mistake when I invested that money. Put the two verbs together as in: I see now why you were being so polite to her because at the time I didn’t recognise her and then I realised she was your boss.
In my experience (with German learners of English), it is “realise” in the sense of “to be/become aware of sth.” and “recognise” in the sense of “identify, acknowledge or admit that sth. is true” that get confused, and indeed there are situations in which the meaning is close:
e.g., back in the 1940s, few people realised (i.e., they were not aware) how dangerous smoking was.
back in the 1940s, the government had not yet recognised that smoking posed a health risk. (in other words, the government had failed to identify the danger for the good of others)
The government has realised that it has to clamp down on teenage drinking. (i.e., in its own mind, it has become aware)
The government has recognised that it has to clamp down on teenage drinking. (i.e., it has acknowledged - perhaps publicly - the need to get tougher)
The example I tend to use for a more basic distinction is:
I realised that a woman was sitting behind me. She was about about my age, but I didn’t recognise her.