I noticed that the bulk modulus often has a negative sign appended to it in order to cancel with a negative change in an object's volume; this allows the bulk modulus to be positive.
However, I noticed that the compression modulus, or Young's Modulus but with respect to compressive forces, does not have a negative sign attached (at least according to what I have seen). Since the change in length of an object is negative when compressive stress occurs, I would assume that, without a negative sign attached to the equation to cancel the negative change in length, the modulus would result in a negative value.
Is there a physical reason for this, if any? What would it be?