Origin: Latin suffix -al
Bisexual has 5 different meanings across 2 categories:
a person who is sexually attracted to both sexes
"As a bisexual woman, she has always been romantically drawn to men and women equally."
A person who is bisexual.
"My friend, who identifies as a person who is bisexual, enjoys dating both men and women."
sexually attracted to both sexes
"After realizing her feelings, she came out as bisexual because she is sexually attracted to both men and women."
Sexually attracted to both men and women (by a narrow definition) or to people of multiple or any genders (by a broad definition; compare pansexual).
"After years of dating only women, she realized her feelings were bisexual when she fell for a man."
In plain English: Bisexual describes someone who is attracted to more than one gender, but not necessarily all of them at the same time or equally.
"Many people are bisexual and find partners both men and women attractive."
Usage: Bisexual describes someone sexually attracted to more than one gender, though this does not require attraction to both men and women specifically as some definitions include all genders. Use the adjective form when describing feelings or identity rather than referring to a specific individual with the noun "a bisexual."
The word bisexual comes from combining the prefix bi- with sexual through French, first appearing in English in 1792. It was originally used specifically to describe plants that possess both male and female reproductive parts.