以-a 结尾的拉丁语n.,词尾变为-ae或-as(少数),
eg: alga/algae(海藻),larva/larvae/larvas(幼虫)
以-ex或-ix结尾的拉丁语n.,在词尾直接加-es,或把-ex或-ix变为-ices
eg: apex/apexes/apices(顶点),index/indexes/indices(索引)
以-is结尾的希腊语n.变-is为-es. eg: analysis/analyses, crisis/crises, basis/bases
以-on或-um结尾的n.变-on或-um为-a,有的可直接在词尾加-s
eg:datum/data, medium/media/mediums, phenomenon/phenomena
变-oo为-ee: eg: foot/feet, tooth/teeth
变-ouse为-ice, eg: mouse/mice, louse/lice(虱子)
以-us结尾的拉丁语n.,变-us为-i,有的可直接在词尾加-es
eg: alumnus/alumni, bacillus/bacilli(杆菌),fungus/fungi/funguses(真菌)