bi-, bin-, bino-, bis-
(Latin: two, twice, double, twofold; a number; it normally functions as a prefix)
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".
2. Occurring every two years; biennial.
A biannual event occurs twice a year; a biennial event takes place once in two years.
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 ["biannual"]), and for the other sense to use the phrase "every two" (every two months; every two weeks; every two years [or in this case, "biennial"]).
Edna's country cousins come to visit on a biannual basis; however, her cousins who live across the ocean come here on biennial trips. It is always great fun to garden together; Jane and Carmen like to plant perennial flowers which will be in bloom whenever their cousins come to visit them.
2. An athletic contest comprising of any two consecutive events.
A bicameral government has two legislative branches or chambers, like the House and the Senate of the United States.
2. Something that happens every two hundred (200) years.