Both can mean 'darse cuenta', but one implies mental understanding and the other sensory perception.
"Realize" is to come to understand or become aware of something you did not know or had not thought about before. The awareness comes from within. "I just realized I forgot" = it just occurred to me that I forgot.
I just realized I left my keys at home.
She realized she was in love with him.
Did you realize how serious this is?
"Notice" is to perceive or detect something with your senses or attention. The perception comes from something external. "Did you notice the sign?" = did you see the sign?
Did you notice anything strange in the room?
She noticed that he was wearing a new tie.
I did not notice the sign.
Common mistake
"I realized a strange smell" is wrong: sensory perception (smelling, seeing, hearing something) uses "notice." "Realize" is for mental understanding, when something clicks in the mind: "I realized I had forgotten my keys."
Trick to remember it
Quick rule
Did you know?
REALIZE has a second meaning completely unrelated to "darse cuenta": "to realize a profit" (to generate or materialize a gain) and "to realize a dream" (to make a dream real). This REALIZE comes from the sense of "to make real", converting something potential into actuality. "Realize your potential" = make your potential real. "The investment realized a 20% return" = the investment generated a 20% return. American English spells it "realize"; British English "realise", both are correct. And NOTICE can also be a noun: "give notice" (to warn or resign formally), "at short notice" (with little warning), "until further notice" (until announced otherwise).
Exercise 1 · Pick the right one
I _____ d that I had left my keys at home when I reached the door.
Exercise 2 · Pick the right one
She _____ d a strange smell coming from the kitchen and went to check.
Exercise 3 · Form the word
One is recalling something yourself, the other is making someone else recall it.
"Above" is at a higher level without contact; "over" implies covering, movement, or crossing.
"Actually" corrects or contrasts an assumption; "really" intensifies or confirms.
'Currently' means 'at the present time'; 'actually' means 'in reality', not 'nowadays'.
Bryan López
Founder of SpeakUP Academy