seriously; in earnest; for real
Adverbial form of 本気, used to describe doing something with genuine intent, effort, or sincerity. Often used in casual speech to emphasize that one is not joking.
本気で日本語を勉強したい。
I seriously want to study Japanese.
彼は本気で怒っている。
He is really angry.
Adverbial form of 本気 (ほんき), a compound of 本 (ほん, 'true' or 'real') and 気 (き, 'spirit' or 'mind'). The exact historical derivation is uncertain, but the combination conveys the idea of 'true spirit' or 'real intent'.