公式 (gōng shì) means 'formula' — a fixed, standardized expression used in mathematics, science, engineering, or even everyday reasoning. The character 公 (gōng) means 'public' or 'common', suggesting something universally accepted and shared; 式 (shì) means 'form', 'pattern', or 'format'. Together, they convey the idea of an established, objective rule or structure that applies consistently across cases.

This word is commonly used in academic, technical, and formal contexts — for example, in math class (e.g., the quadratic formula), physics (e.g., Newton’s laws expressed as formulas), or even in business (e.g., a pricing formula). It is not used for informal rules or personal habits. Unlike English 'formula', 公式 rarely carries metaphorical or culinary meanings (e.g., no 'secret formula for success' in casual speech — use 方法 or 秘诀 instead).