(mathematics) equivalence class

concept, general idea

important, significant

importance, consequence, significance

extraordinary, unusual

emergency

very; extremely / exceedingly; tremendously

mathematics (field of study)

kind, sort, type, class, genus, order, family / similar example, parallel

kind, sort, type, the like / a similar thing, parallel / (taxonomy) a conventional grouping that corresponds to a class or an order / (logic) Short for 類概念 (ruigainen).