改正【かいせい】
revision, amendment, alteration
改革【かいかく】
reform, reformation, reorganization
改善【かいぜん】
betterment, improvement, kaizen (Japanese business philosophy of continuous improvement)
改造【かいぞう】
remodeling, remodelling, reconstruction, conversion, alteration, renovation, modification, reshuffling (e.g. a cabinet), reorganization, restructuring, modding
改憲【かいけん】
constitutional change, revising the constitution
改良【かいりょう】
improvement, reform
改選【かいせん】
re-election
改める【あらためる】
to change, to alter, to revise, to replace, to reform, to correct, to mend, to improve, to examine, to check, to inspect, to do properly, to do formally
改築【かいちく】
structural alteration (of a building), reconstruction, rebuilding, remodelling, remodeling
改札【かいさつ】
examination of tickets, ticket gate, ticket barrier
改新【かいしん】
reformation
改訂【かいてい】
revision (of text), alteration, change
改めて【あらためて】
another time, again, over again, once again, anew, formally, especially, intentionally, deliberately
改訂版【かいていばん】
revised edition
改名【かいめい】
name change
改まる【あらたまる】
to be renewed, to change, to be improved, to be reformed, to be revised, to be corrected, to stand on ceremony, to be formal, to take a turn for the worse (of an illness), to take a serious turn
改宗【かいしゅう】
religious conversion