n.
     - a circumstance, fact, or influence that contributes to a result. 
▸Biology  a gene that determines a hereditary characteristic.
 - Mathematics  a number or quantity that when multiplied with another produces a given number or expression. 
▸a number or algebraic expression by which another is exactly divisible.
 - a level on a scale of measurement:
 a protection factor of 15.
 - Physiology  any of a number of substances in the blood which are involved in coagulation.
 - a business agent. 
▸a company that buys a manufacturer's invoices at a discount and takes responsibility for collecting the payments due on them.
 ▸Scottish a land agent or steward.
 
v.
   - 
(factor something in/out)
 include (or exclude) something as a relevant element when making a decision.
 - Mathematics  another term for factorize.
 - sell (one's receivable debts) to a factor.
 
 
  Derivative
  
  Etymology
  ME (meaning ‘doer’, also in the Scots sense ‘agent’): from Fr. facteur or L. factor, from fact-, facere ‘do’.