一般加s:attack, donate, occur, recover, respond, clap, escape, ache, survive
以s, x, sh, ch, o结尾加es:focus, fix, crash, flash, establish, approach, attach, go, do
辅音字母+y结尾,y→ies:study, carry, fly, worry, apply, fancy
特殊变化:have→ has, be→ am/is/are