factor in

factor space

A space obtained from another by identification of points that are equivalent to one another in some equivalence relation.

fudge factor

A quantity introduced to compensate for uncertainty.

gut factor

The emotional dimension of decision-making. A person's subjective (often almost visceral) feelings about what is right or wrong, good or bad.

X factor

An unknown or hard-to-define influence; a factor with unknown or unforeseeable consequences.