정진해요 · 정진했어요 · 정진할 거예요 · 정진하세요
to devote oneself to, to strive diligently
Example
그는 은퇴 후에도 연구에 정진하고 있어요.
Even after retiring, he is devoting himself to his research.
Word parts
정 pure+진 advance
Literally 'advance with purity' — originally Buddhist striving toward enlightenment.