#formula__expression  a group of symbols that make a mathematical statement
  supertype:  mathematical_statement  a statement of a mathematical relation
  subtype:  sentential_function  formal expression containing variables; becomes a sentence when variables are replaced by constants
  subtype:  primitive.formula  a mathematical expression from which another expression is derived
  subtype:  exponential_expression__exponentialexpression  a mathematical expression consisting of the constant e raised to some power

No statement uses or specializes formula; click here to add one.