equation vs extent

equation

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

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

  • 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. 

extent

noun
  • A range of values or locations. 

  • A former tent; something (or someone) that was a tent but no longer is 

  • The valuation of property. 

  • A contiguous area of storage in a file system. 

  • The space, area, volume, etc., to which something extends. 

  • A writ directing the sheriff to seize the property of a debtor, for the recovery of debts of record due to the Crown. 

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