| callous(verb, adjective, dull, develop, rough) |
| drill(noun, verb, study, develop, tell) |
| enure |
| familiarise(verb, habituate) |
| caseharden(impulse, insensibility) |
| confirm(verb, prepare, endure, adjust, familiarize) |
| exercise(noun, verb, study, develop, improve) |
| naturalize(verb, tell, condition, case, explain) |
| tame(verb, study, develop, improve, prepare) |
| teach(verb, study, dull, develop, rough) |
| temper(noun, verb, prepare, strengthen, harden) |
| accustomed |
| become effective(verb, expression, idiom, law, order) |
| become operative(verb, expression, idiom, law, order) |
| breed(preparation, teaching) |
| brutalize(verb, dull, develop, rough, adjust) |
| callus(verb, dull, develop, rough, adjust) |
| coach(verb, study, develop, tell, improve) |
| come into force(verb, expression, idiom, law, order) |
| develop(verb, study, dull, rough, improve) |