【词根含义】：计算,思考
【词根来源】：来源于拉丁语动词reor, reri, ratus, sum(计算,思考)。
【同源单词】：irrational, overrate, rate, ratify, rating
【词根含义】：过分,在…上
【同源单词】：overcast, overcome, overdraft, overdraw, overdue