Two readings: kàn (4th tone, this entry) = look / read / watch / visit / consider; kān (1st tone, sister entry) = guard / look after. As a rule of thumb, when
看 means "watch over to protect" (a door, a house, a patient, prisoners), it's kān; everywhere else it's kàn. Compounds:
看电影 kàn,
看护 kān.