extra arm外臂, 可变臂
extraadj.额外的n.额外之物;临时演员adv.特别地
extraditable fugitives.可引渡的逃犯
extra-curriculum sports课外体育活动
extra dietary requirement特别膳食需要
Extraeorporeal shock wave体外冲击波
extra deep foundation pit超深基坑
extra-dense flint glass特重火石玻璃
extraterrestrial disposal地球外放射性废物处置法
extraparotid lymph glands腮腺外淋巴结
extracorporeal experiment体内实验
extraordinarily difficult特别困难