formula vs usage

formula

noun
  • A formal statement of doctrine. 

  • Any mathematical rule expressed symbolically. 

  • A symbolic expression of the structure of a compound. 

  • A formulation; a prescription; a mixture or solution made in a prescribed manner; the identity and quantities of ingredients of such a mixture. 

  • A syntactic expression of a proposition, built up from quantifiers, logical connectives, variables, relation and operation symbols, and, depending on the type of logic, possibly other operators such as modal, temporal, deontic or epistemic ones. 

  • A plan or method for dealing with a problem or for achieving a result. 

usage

noun
  • A custom or established practice. 

  • Custom, tradition. 

  • The established custom of using language; the ways and contexts in which spoken and written words are used, especially by a certain group of people or in a certain region. 

  • The act of using something; use, employment. 

How often have the words formula and usage occurred in a corpus of books? (source: Google Ngram Viewer )