Bi

Bi is the chemical symbol for bismuth, a brittle, silvery‑white post‑transition metal with atomic number 83. Bismuth forms a distinctive oxide surface that can display iridescent rainbow colors. It is highly diamagnetic and has relatively low thermal and electrical conductivity for a metal. Bismuth occurs mainly in minerals such as bismuthinite and bismite and is rarely found in native form. It melts at 271.4°C and boils at 1564°C. Bismuth is used in low‑melting alloys, lead‑free solders, and certain cosmetics pigments. It also appears in medicines as bismuth subsalicylate, the active ingredient in some stomach remedies. Bismuth compounds are generally considered among the less toxic heavy metals. The heaviest naturally occurring isotope, bismuth‑209, long regarded as stable, is now understood to be extremely weakly radioactive with a very long half‑life.

Bi is also a common shorthand for bisexual, an orientation characterized by attraction to more than one gender. It is used within LGBTQ+ communities and in academic and popular discourse. People who identify as bi may experience attraction toward two or more genders, though experiences vary and individuals may identify in different ways over time. Bisexuality has faced stereotypes and erasure in various contexts, but visibility and understanding have grown, contributing to greater inclusion. It is distinct from related terms such as pansexual and from notions of fluidity that apply differently to individuals.

Bi‑ is a Latin prefix meaning two or twice. It is used across disciplines to denote duality or pairing, as in bicycle, bilateral, and binary, and appears in many terms in science, mathematics, and everyday language.