Mathematical Bold Capital Beta

In Word, type 1D6A9 and press Alt+X.

Word replaces the hexadecimal input with 𝚩. This is Microsoft Word's hex-input method; other systems may provide different Unicode entry tools.

What does bold beta mean in math?

It marks Greek capital beta in bold mathematical style.

Treat it as a variable whose value or job is set where the author defines it. Some fields put vectors (quantities with magnitude and direction) in bold type, but uppercase beta is not a vector symbol by rule.

Mathematical style can change what a variable denotes, so Unicode gives this form a separate character. These mathematical alphabets are intended for mathematical or technical writing, where the distinction has a job to do.

How did bold Greek letters enter math?

Bold mathematical type appeared long before Unicode.

In 1881, mathematician J. Willard Gibbs wrote that small Greek letters would stand for vectors (quantities with magnitude and direction), while small Latin letters stood for scalars (quantities without direction). In 1901, E. B. Wilson's vector-analysis textbook used bold type for vectors and ordinary type for scalars. Later authors also used type styles to distinguish other mathematical objects, so these examples show a convention's development rather than one fixed meaning for 𝚩.