death anniversary; anniversary of a person's death
Commonly used as a suffix after a number, e.g. 一周忌 (first anniversary of death), 三周忌 (third anniversary). Also used as a standalone noun in formal contexts.
See also: 回忌
Next month is the third anniversary of my grandfather's death.
We held a memorial service on the first anniversary of his death.
second anniversary of a death
周 (cycle, circumference) + 忌 (mourning, anniversary of death). The combination refers to the cyclical return of the death anniversary.