Definition of “notice” - Learner’s Dictionary

notice

verb [ I, T ] us uk /ˈnəʊtɪs/
Simon was so absorbed in his computer game, he didn't notice me come in.Did you notice anything odd about his behaviour?I noticed a small spot of oil on my jacket.Scientists have noticed a drop in the number of song birds in Britain.I called airport security after noticing a suspicious-looking package.

to see something and be aware of it:

If the sign's too small, no one will notice it.
Do you think he'll notice my new hair style?
[ + (that) ] I noticed that he walked with a limp.

(Definition of “notice verb” from the Cambridge Learner's Dictionary © Cambridge University Press)