单三：⑴直接加s,例：run-runs,draw-draws,see-sees
⑵在s,x,sh,ch等后加es,例：wash-washes,watch-watches,dress-dresses
⑶在y结尾的单词后：①y前是元音字母,直接加s ,例：buy-buys,enjoy-enjoys
②y前是辅音字母,变y为i加es,例：fly-flies,try-tries,study-studies