Meaning of “ah” - Learner’s Dictionary

ah

exclamation us uk /ɑː/
SHOW FEELING

used to show sympathy or to show pleasure at seeing a baby or attractive animal:

Ah, you poor thing!
Ah, look at that little kitten!
UNDERSTAND

used to show that you have just understood something:

Ah, now I see what you're saying!

(Definition of “ah” from the Cambridge Learner’s Dictionary © Cambridge University Press)