Worded rule, definition, or relationship between different variables/quantities written using letters, constants, and an equals sign. Formulas on their own cannot be solved, but once substituting numbers to replace variables in formulas, then equations can be formed, which can subsequently be solved.
E.g: “Weight, w, is mass, m, multiplied by gravitational field strength, g. OR w = mg”.
if w = 50N and g = 10N/kg, find m.
w = mg → 50 = 10m → m = 5kg