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• bi
  bi

  adjective

  bisexual.
• Bi
  Bi

  bismuth.
• BI
  BI

  abbreviation

  built-in.
• bi-
  bi-

  a combining form meaning “twice,” “two,” used in the formation of compound words.

bi

¹ American  

[bahy] / baɪ /

adjective

bis, plural bi's plural

1. Slang. bisexual.

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Bi ² American  

Symbol, Chemistry.

1. bismuth.

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BI ³ American  

abbreviation

BI's plural

1. built-in.

2. business intelligence.

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bi- ⁴ American  

1. a combining form meaning “twice,” “two,” used in the formation of compound words.

   bifacial; bifarious.

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bi- ⁵ American  

1. variant of bio-, especially before a vowel.

   biopsy.

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bi- ¹ British  

combining form

1. two; having two

   bifocal

2. occurring every two; lasting for two

   biennial

3. on both sides, surfaces, directions, etc

   bilateral

4. occurring twice during

   biweekly

5. 1. denoting an organic compound containing two identical cyclic hydrocarbon systems

      biphenyl

   2. (rare in technical usage) indicating an acid salt of a dibasic acid

      sodium bicarbonate

   3. (not in technical usage) equivalent of di- 1

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Bi ² British  

symbol

1. bismuth

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bi ³ British  

/ baɪ /

adjective

1. slang short for bisexual bisexual

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bi- ⁴ British  

combining form

1. a variant of bio-

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bi ⁵ British  

abbreviation

1. Burundi

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Usage

What does bi- mean? Bi- is a combining form used like a prefix, and it means “two” or “twice.” It is often used in scientific terms, but it crops up in everyday language as well. Bi- comes from Latin bis, meaning “twice, doubly.” The Greek equivalent of this combining form is di-, as in diacid. What are variants of bi-?Bi- is related to the combining form bin- and is used with some words or word elements beginning with vowels. These two forms have similar origins, and for that reason, the difference between the two is a small yet important nuance: bi- often means “twice,” while bin- typically means “double.”Want to know more? Read our Words That Use bin- article.

Commonly Confused

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 ).

Etymology

Origin of bi¹

By shortening

Origin of bi-⁴

< Latin, combining form of bis; see twice

Example Sentences

Two replication forks are formed at the origin of replication and these get extended bi- directionally as replication proceeds.

From Textbooks • Jun. 9, 2022

Kids who grow up bi- or even trilingual may appear delayed in any one language, simply because they’re splitting the number of words they know between languages.

From Slate • Nov. 14, 2019

“I don’t know, bi- or pansexual,” Katie said.

From New York Times • May 24, 2018

About 246,000 of the people who took the test had grown up speaking only English, while the rest were bi- or multilingual.

From BBC • May 1, 2018

Foliolate, having leaflets; the number indicated by the Latin prefixes, bi-, tri-, etc.

From The Wild Flowers of California: Their Names, Haunts, and Habits by Parsons, Mary Elizabeth