plan vs proposal

plan

noun
  • A method; a way of procedure; a custom. 

  • A drawing showing technical details of a building, machine, etc., with unwanted details omitted, and often using symbols rather than detailed drawing to represent doors, valves, etc. 

  • A subscription to a service. 

  • A set of intended actions, usually mutually related, through which one expects to achieve a goal. 

  • A two-dimensional drawing of a building as seen from above with obscuring or irrelevant details such as roof removed, or of a floor of a building, revealing the internal layout; as distinct from the elevation. 

verb
  • To create a plan for. 

  • To intend. 

  • To design (a building, machine, etc.). 

  • To make a plan. 

proposal

noun
  • A scheme or design 

  • The terms or conditions proposed 

  • The document on which such a thing is written. 

  • The offer by a party of what he has in view as to an intended business transaction, which, with acceptance, constitutes a contract. 

  • The act of asking someone to be one's spouse; an offer of marriage 

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