noun
commemorative plaque; stone monument
A stone monument or plaque bearing an inscription to commemorate a person, event, or achievement.
公園に戦没者を追悼する記念碑が建てられた。
A monument was erected in the park to commemorate the war dead.
その記念碑には彼の功績が刻まれている。
His achievements are inscribed on the monument.
碑 is a broader term for any stone monument or tombstone; 記念碑 is a type of 碑 with a commemorative purpose.
Compound of 記念 (commemoration) and 碑 (stone monument).