In a VX system, delta (also written as Delta or δ) refers to a function whose output generalizes the results and performance of the system to a single unitless fraction. It also is often used to refer to the value of the function, or the maximum possible value attainable under given conditions.

Delta is most commonly used in quantum applications of VX, in which the Uncertainty Principle prevents any 100% accurate readings to be made of subatomic systems. Therefore, any operation must be run billions of times in the tertiary computer grid in order to deduce a mathematical average based on the varying results. In this application, delta refers to the perceived accuracy of this average. The maximum accuracy in a three-dimensional spatial environment is 88%, or δ=0.88 (Yalgeth's Limit).