delta

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'.