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’.*