Beta symbol β

• Statistics: β is the probability of a Type II error (missing a real effect), so a test’s power is 1 − β. In regression, β₀, β₁ and so on are the coefficients.
• Finance: beta measures how much a stock tends to move relative to the overall market. A beta of 1 means it tends to move with the market.
• Physics: beta particles are electrons or positrons emitted in beta decay.
• Medicine and nutrition: beta-blockers, β-carotene, β-lactam antibiotics.
• Software: a beta is a test version released before the final product, usually feature-complete but not yet polished.
• Geometry: the second angle of a triangle, after α.

The German letter ß looks like β but is unrelated. It is a Latin letter, historically a ligature of a long s with s or z, and it spells words like Straße. In many fonts the two are hard to tell apart, which leads to three common mistakes:

• On a Mac, Option+S types ß, not β. People who use that shortcut for “beta” end up with a German letter in their documents.
• On Windows, the old Alt+225 code also gives ß. In the DOS-era code page 437, one position served for both letters, and today it maps to ß.
• In data and search, ß and β are different characters, and uppercasing typically turns ß into SS.

The capital beta Β looks exactly like a Latin B but is a separate character, so don’t use it to spell English words.

• Word: in an equation (Alt+=), type \beta and press space.
• LaTeX: \beta.
• Mac: open the Character Viewer with Control+Command+Space and search “beta,” or add a text replacement such as “betaa” → β in System Settings > Keyboard.
• iPhone and Android: add the Greek keyboard; β is where B is on a US keyboard.
• Excel: =SLOPE() returns a regression slope, and =LINEST() returns all the coefficients, the βs you report in a results table.