opposite category
category constructed from another category C, whose objects are the same as those of C, whose morphisms from X to Y are the same as the morphisms in C from Y to X
en-US/ˈɑpzət ˈkædəˌɡoʊɹi/
en-GB/ˈɒpəzɪt kætɪɡəɹiː/
category constructed from another category C, whose objects are the same as those of C, whose morphisms from X to Y are the same as the morphisms in C from Y to X