equation vs proportion

equation

noun
  • An assertion that two expressions are equal, expressed by writing the two expressions separated by an equal sign; from which one is to determine a particular quantity. 

  • The act or process of equating two or more things, or the state of those things being equal (that is, identical). 

  • A small correction to observed values to remove the effects of systematic errors in an observation. 

proportion

noun
  • A statement of equality between two ratios. 

  • The relation of one part to another or to the whole with respect to magnitude, quantity, or degree. 

  • Harmonious relation of parts to each other or to the whole. 

  • A quantity of something that is part of the whole amount or number. 

  • Size. 

  • Proper or equal share. 

verb
  • To form symmetrically. 

  • To set or render in proportion. 

  • To divide into proper shares; to apportion. 

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