后缀：-ce [副词后缀]

表示“...次”、“自...”、“从...”

once 一次

hence 因此，从今以后

twice 二次

thence 自那里，从那时起

thrice 三次

whence 从何处，由此

词根词缀：bi-, bin-, bino-, bis-

【来源及含义】Latin: two, twice, double, twofold; a number; it normally functions as a prefix

【相关描述】This bi- is used before s, c, or a vowel. Don't confuse this bi- with another one which means "life".

All words except biennial referring to periods of time and prefixed by bi- are potentially ambiguous. Since bi- can be taken to mean either "twice each" or "every two", a word like "biweekly" can be understood as "twice each week" or "every two weeks".

【同源单词】biacid, biangular, biannual, biannual, biarchy, biarticulate

词根词缀：di-, dicho-, dich-

【来源及含义】Greek: number two; twice, divided, double; unalike; a number used as a prefix

【同源单词】diacanthous, diacid, diadelphous, dianthous, diarch, diarchy

词根词缀：semi-

【来源及含义】Latin: half, partly, twice

【同源单词】semi-acid, semi-amplexicaul, semiannual, semiannually, semiaquatic, semiarid