Āi dào is a formal, solemn verb meaning 'to mourn' or 'to hold a memorial service' for someone who has died. The first character 哀 (āi) conveys deep sorrow, grief, or lamentation, often associated with loss and respect; the second character 悼 (dào) specifically refers to mourning the dead and expressing reverence for the deceased. Together, they form a compound that emphasizes respectful, ritualized grief — not casual sadness, but a dignified, often public or collective act of remembrance.

This word is commonly used in official announcements, news reports, memorial ceremonies, and formal writing. It appears frequently when commemorating national figures, victims of disasters, or respected elders. While it can be used transitively (e.g., 哀悼逝者), it’s rarely used in informal speech among friends or family — where simpler terms like 难过 (nánguò) or 悲伤 (bēishāng) are more natural. Its tone is consistently serious and reverent.