fac·tor (făk'tər)
n.

1. One that actively contributes to an accomplishment, result, or process: "Surprise is the greatest factor in war" (Tom Clancy). See synonyms at element.
2. 1. One who acts for someone else; an agent.
   2. A person or firm that accepts accounts receivable as security for short-term loans.
3. Mathematics. One of two or more quantities that divides a given quantity without a remainder. For example, 2 and 3 are factors of 6; a and b are factors of ab.
4. A quantity by which a stated quantity is multiplied or divided, so as to indicate an increase or decrease in a measurement: The rate increased by a factor of ten.
5. A gene. No longer in technical usage.
6. Physiology. A substance that functions in a specific biochemical reaction or bodily process, such as blood coagulation.

tr.v., -tored, -tor·ing, -tors.
To determine or indicate explicitly the factors of.

phrasal verb:

factor in

1. To figure in: We factored sick days and vacations in when we prepared the work schedule.

[Middle English factour, perpetrator, agent, from Old French facteur, from Latin factor, maker, from facere, to make.]

factorable fac'tor·a·ble adj.
factorship fac'tor·ship' n.

---

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

---