san
词根含义：to heal;
助记词：insane，in（not，否定前缀）+san（治愈）+e=》没有治愈的=》头脑不清的
同根词：sane, sanitate, insanity, sanatorium, insanitary

med, medic
词根含义：to heal;
助记词：remedy，re（再次）+med（治愈）+y=》再次治愈的药物=》补救措施
同根词：remedy, irremediable, medicine, medical, medicament, medicate

medi
词根含义：middle;
助记词：median，medi（中间）+an（形容词后缀）=》中央的
同根词：immediate, intermediate, median, mediate, medieval, mediocre, mediterranean, medium

centr
词根含义：the middle point;
助记词：centre;
同根词：central, centre, centric, centrifugal, centripetal, concentrate, concentric, decentralize, eccentric

总结今天的词根可以分为三组

to heal

san
med, medic

易混词根辨析

med, medic
medi

middle

medi
centr

谈及heal想到了实习医生格蕾中Doctor Shepherd在手术前的口头禅：

It's a beautiful day to save lives !

不知Doctor Shepherd意外去世后有多少人弃剧……

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