noun
determination; esprit de corps; morale
Refers to a group's shared fighting spirit, determination, or morale, often in military, sports, or organizational contexts.
チームの志気を高めるために、監督は熱いスピーチをした。
The coach gave a passionate speech to boost the team's morale.
敗戦後も、兵士たちの志気は衰えなかった。
Even after the defeat, the soldiers' morale did not wane.
士気 is the more common spelling for 'morale' or 'fighting spirit', while 志気 is a variant that emphasizes personal determination or will.
Compound of 志 (will, aspiration) and 気 (spirit, energy). The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning of group morale and determination.