1With all one's effort or might; giving one's very best at something. Often used adverbially (一生懸命 + verb, e.g. 一生懸命勉強する 'to study very hard') and also as a na-adjective (一生懸命な人 'a hard-working person').
試験に合格するために一生懸命勉強した。
I studied very hard to pass the exam.
彼は一生懸命働いて家族を支えている。
He works with all his might to support his family.
子供たちは一生懸命練習して、ついに大会で優勝した。
The children practiced with all their might and finally won the competition.
一生懸命なところが彼女の一番の魅力だ。
Her earnest, hard-working nature is her biggest charm.