Definitions of formula:

• noun:   a group of symbols that make a mathematical statement
• noun:   a conventionalized statement expressing some fundamental principle
• noun:   a representation of a substance using symbols for its constituent elements
• noun:   a liquid food for infants
• noun:   (mathematics) a standard procedure for solving a class of mathematical problems

  Example: "He gave us a general formula for attacking polynomials"

• noun:   directions for making something
• noun:   something regarded as a normative example

  Example: "His formula for impressing visitors"