Patrick Ward 
Business Definition of “What's the delta”
The expression 'what's the delta' and variations are commonly used in business to refer to the difference between two things, or the rate of change between two states, depending on the context.
What Does “What’s the delta” Mean?
Delta’ is commonly abused as a corporate buzzword by consultants, who believe (correctly) that if they refuse to use plain language, they will get paid more.
Use case example
If this campaign works, what’s the delta for revenue?
What this really means is: “if this campaign works, how much revenue will it add to our existing revenue.”
Honestly, it’s a bit of a buzzword which is mostly used by consultants and middle-managers.
For example, if X represents the temperature of a cupcake, we could construct a formula to determine the difference in temperature of the cupcake from when placed in the oven (X1) and after 20 minutes (X2): ΔX = X2-X1. ΔX is the change in temperature of the cupcake. If you were a consultant at a prestigious consulting firm, you would describe this as ‘the delta of the baked good, between two key states.’
