n. A small quantity, but not as small as epsilon. The jargon usage of delta and epsilon stems from the traditional use of these letters in mathematics for very small numerical quantities, particularly in ‘epsilon-delta’ proofs in limit theory (as in the differential calculus). The term delta is often used, once epsilon has been mentioned, to mean a quantity that is slightly bigger than epsilon but still very small. “The cost isn’t epsilon, but it’s delta” means that the cost isn’t totally negligible, but it is nevertheless very small. Common constructions include within delta of —, within epsilon of —: that is, ‘close to’ and ‘even closer to’.
…or, at least, I’m guessing it’s something closely related to that. Certainly it’s common in math to use δ for a small quantity (both in this context, and in the “incremental change” context, which is sense 1 at the link).
@january1may sniped me on this one, but that, basically, yeah.
It was techjargon adopted into my vocabulary long before I learned about epsilon-delta limits, etc., and I usually make delta-fine distinctions before moving onward to epsilon-fine distinctions, so δ is the one I default to first.
