extent vs 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. 

quantity

noun
  • A specific measured amount. 

  • Length of sounds. 

  • Indicates that the entire preceding expression is henceforth considered a single object. 

  • A fundamental, generic term used when referring to the measurement (count, amount) of a scalar, vector, number of items or to some other way of denominating the value of a collection or group of items. 

  • An indefinite amount of something. 

  • A considerable measure or amount. 

  • Property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed as number and a reference. 

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