世紀
せいき · seiki · JLPT N3 · noun
century
⏳ 世紀 = generation + chronicle: a record that spans many generations
世 means world or generation, as in 世界 (world). 紀 means a record or era, as in 紀元 (the start of an era). A 世紀 is a chronicle of generations, which works out to a hundred years. 21世紀 is the 21st century.