nhấm
verb

to gnaw at, to nibble

nhẩm
verb

to read silently (to try to memorise); to say under one's breath

nhắm
verb

to close (eyes)
(shooting, archery) to aim, especially with one eye closed
(figuratively, usually followed by tới to đến) to be trying to reach an aim
(alcoholism) to eat at a leisure pace with alcohol