Used for annual commemorations, often in formal or institutional contexts such as founding anniversaries.
Next month, the company's 50th anniversary celebration will be held.
annual festival
imperial memorial ceremony held on fixed anniversaries
centenary; centennial celebration
prayer service for a good crop
harvest festival; fertility festival
jubilee; semicentennial; 50th anniversary celebration
Compound of 年 (year) and 祭 (festival, celebration), literally 'year festival'. The exact historical derivation is uncertain, but it is conventionally used for anniversary events.