See more synonyms for factor on Thesaurus.com
  1. one of the elements contributing to a particular result or situation: Poverty is only one of the factors in crime.
  2. Mathematics. one of two or more numbers, algebraic expressions, or the like, that when multiplied together produce a given product; a divisor: 6 and 3 are factors of 18.
  3. Biochemistry. any of certain substances necessary to a biochemical or physiological process, especially those whose exact nature and function are unknown.
  4. a business organization that lends money on accounts receivable or buys and collects accounts receivable.
  5. a person who acts or transacts business for another; an agent.
  6. an agent entrusted with the possession of goods to be sold in the agent's name; a merchant earning a commission by selling goods belonging to others.
  7. a person or business organization that provides money for another's new business venture; one who finances another's business.
  8. factor of production.
  9. Scot. the steward or bailiff of an estate.
verb (used with object)
  1. Mathematics. to express (a mathematical quantity) as a product of two or more quantities of like kind, as 30 = 2·3·5, or x2y2 = (x + y) (x − y).Compare expand(def 4a).
  2. to act as a factor for.
verb (used without object)
  1. to act as a factor.
Verb Phrases
  1. factor in/into, to include as an essential element, especially in forecasting or planning: You must factor insurance payments into the cost of maintaining a car.

Origin of factor

1400–50; late Middle English facto(u)r < Latin factor maker, perpetrator, equivalent to fac(ere) to make, do + -tor -tor
Related formsfac·tor·a·ble, adjectivefac·tor·a·bil·i·ty, nounfac·tor·ship, nounsub·fac·tor, nounun·der·fac·tor, nounun·fac·tor·a·ble, adjectiveun·fac·tored, adjective

factor VIII

Origin of factor VIII

First recorded in 1960–65

factor IX

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for factor


  1. an element or cause that contributes to a result
  2. maths
    1. one of two or more integers or polynomials whose product is a given integer or polynomial2 and 3 are factors of 6
    2. an integer or polynomial that can be exactly divided into another integer or polynomial1, 2, 3, and 6 are all factors of 6
  3. (foll by identifying numeral) med any of several substances that participate in the clotting of bloodfactor VIII
  4. a person who acts on another's behalf, esp one who transacts business for another
  5. commerce a business that makes loans in return for or on security of trade debts
  6. former name for a gene
  7. commercial law a person to whom goods are consigned for sale and who is paid a factorage
  8. (in Scotland) the manager of an estate
  1. (intr) to engage in the business of a factor
See also factor in
Derived Formsfactorable, adjectivefactorability, nounfactorship, noun

Word Origin for factor

C15: from Latin: one who acts, from facere to do


Factor (sense 1) should only be used to refer to something which contributes to a result. It should not be used to refer to a part of something such as a plan or arrangement; instead a word such as component or element should be used

factor VIII

  1. a protein that participates in the clotting of blood. It is extracted from donated serum and used in the treatment of the commonest type of haemophilia, in which it is absent
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for factor

early 15c., "agent, deputy," from Middle French facteur "agent, representative," from Latin factor "doer or maker," agent noun from past participle stem of facere "to do" (see factitious). Sense of "circumstance producing a result" is from 1816.


1610s, "act as an agent," from factor (n.). The use in mathematics is attested from 1837. Related: Factored; factoring.

Online Etymology Dictionary, © 2010 Douglas Harper

factor in Medicine


  1. One that contributes in the cause of an action.
  2. A mathematical component that by multiplication makes up a number or expression.
  3. A gene.
  4. A substance, such as a vitamin, that functions in a specific biochemical reaction or bodily process, such as blood coagulation.

factor VIII

  1. A factor in the clotting of blood, a deficiency of which is associated with hemophilia A.antihemophilic factor antihemophilic globulin antihemophilic globulin A proserum prothrombin conversion accelerator

factor IX

  1. A factor in the clotting of blood necessary for the formation of intrinsic blood thromboplastin; a deficiency of it causes hemophilia B.antihemophilic globulin B Christmas factor
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

factor in Science


  1. One of two or more numbers or expressions that are multiplied to obtain a given product. For example, 2 and 3 are factors of 6, and a + b and a - b are factors of a2 - b2.
  2. A substance found in the body, such as a protein, that is essential to a biological process. For example, growth factors are needed for proper cell growth and development.
  1. To find the factors of a number or expression. For example, the number 12 can be factored into 2 and 6, or 3 and 4, or 1 and 12.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.