caer (en la cuenta): comprender, darse cuenta de u ocurrírsele algo a alguien.
-Un día lo vi salir del portal del piso de mi novia, y entonces caí en la cuenta: estaban liados — One day I saw him leaving my girlfriend's flat, and I suddenly realized/ it suddenly occurred to me what was going on: they were seeing each other
-¿Por qué no les recomendaste ese hotel? -No caí — Why didn't you recommend that hotel to them? -It didn't occur to me/ I forgot
-¿Te acuerdas del nombre del bar? -Pues, ahora mismo no caigo — Can you remember the name of the bar? -I can't think of it right now
-Acabo de caer en (la cuenta de) que Juan no estuvo ese día — It's just dawned on me that Juan wasn't there that day
