All 4 Uses of

factor
in
The Hound of the Baskervilles

There is Mr. Frankland, of Lafter Hall, who is also an unknown factor, and there are one or two other neighbours.
Chpt 6 *

factor = something that affects a result or outcome

But, first of all, I must keep you in touch with some of the other factors in the situation.
Chpt 8

factors = things that affect a result or outcome

And yet this new factor must surely arrest his attention and renew his interest.
Chpt 10

factor = thing that affects a result or outcome

As it is, I have been able to get about as I could not possibly have done had I been living in the Hall, and I remain an unknown factor in the business, ready to throw in all my weight at a critical moment.
Chpt 12

Definitions:

(1) (factor as in: It was the deciding factor.)
something that affects a result or outcome

You also may encounter x-factor or x factor--meaning "the most important thing that influences a result or outcome."
(2) (factor as in: factor it into your thinking)
include consideration of
(3) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

See a comprehensive dictionary for other meanings. Less common meanings include one that has to do with units of measurement. More specialized meanings are used in fields including mathematics, business, finance, biology, and grammar.