memorial ceremony; commemorative ceremony
A formal event held to honor and remember a person, group, or historical event.
A memorial ceremony was held for the war dead.
Many guests attended the commemorative ceremony.
記念式 is a shorter, slightly less formal term for a commemorative ceremony, while 記念式典 emphasizes a more elaborate, formal event.
追悼式 specifically refers to a memorial service for the deceased, focusing on mourning, whereas 記念式典 can also celebrate an anniversary or achievement.
Compound of 記念 (commemoration, memory) and 式典 (ceremony, ritual). The word is a straightforward Sino-Japanese compound.