:delta: n. 1. [techspeak] A quantitative change, especially a small
or incremental one (this use is general in physics and
engineering). "I just doubled the speed of my program!" "What
was the delta on program size?" "About 30 percent." (He
doubled the speed of his program, but increased its size by only 30
percent.) 2. [UNIX] A {diff}, especially a {diff} stored
under the set of version-control tools called SCCS (Source Code
Control System) or RCS (Revision Control System). 3. 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'.
-- The AI Hackers Dictionary
