WordNet sense 1 (a branch of knowledge):

bailiwick, field, study, subject, subject, branch of knowledge, field of study, subject area, subject field

WordNet sense 2 (train by instruction and practice; especially to teach self-control):

check, condition, train

WordNet sense 3 (punish in order to gain control or enforce obedience):

correct, sort out

WordNet sense 4 (the act of punishing):

correction