A formal, somewhat academic term for selfless concern for others. In everyday speech, 利他主義 (りたしゅぎ) or 利他 (りた) are more common.
Altruism can sometimes involve self-sacrifice.
His actions are based on pure altruism.
More common term for altruism; 愛他主義 is less frequent and slightly more literary.
Shorter, everyday word for altruism or selflessness; 愛他主義 is more formal and explicit.
altruist
Compound of 愛 (あい, 'love'), 他 (た, 'other'), and 主義 (しゅぎ, '-ism'). The exact origin is uncertain, but it likely follows the pattern of 利他主義 (りたしゅぎ) as a direct translation of Western 'altruism'.