只能先背了可数名词变复数的九种方式\x0d\x0d\x0d\x0d\x0d\x0d7)某些外来词变复数：datum→data, medium→media, bacterium→bacteria, curriculum→curricula, criterion→criteria, phenomenon→phenomena. (um/on→a)analysis→analyses, basis→bases, crisis→crises, diagnosis→diagnoses.(is→es )