bi-

bi-¹

a combining form meaning "twice," "two," used in the formation of compound words: bifacial; bifarious. Cf. bin-.

[ < L, comb. form of bis; see TWICE]

Usage. All words except biennial referring to periods of time and prefixed by BI-¹ 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." To avoid confusion, it is better to use the prefix SEMI- to mean "twice each" (semiannual; semimonthly; semiweekly) or the phrase twice a or twice each (twice a month; twice a week; twice each year), and for the other sense to use the phrase every two (every two months; every two weeks; every two years).

bi-²

var. of bio-, esp. before a vowel: biopsy.

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