1. [n]  the 4th letter of the Greek alphabet
2. [n]  a low triangular area where a river divides before entering a larger body of water

Delta
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1. \Del"ta\, n.; pl. {Deltas}. [Gr. de`lta, the name of the
   fourth letter of the Greek alphabet (the capital form of
   which is [Delta], Eng. D), from the Ph[oe]nician name of the
   corresponding letter. The Greeks called the alluvial deposit
   at the mouth of the Nile, from its shape, the Delta of the
   Nile.]
   A tract of land shaped like the letter delta ([Delta]),
   especially when the land is alluvial and inclosed between two
   or more mouths of a river; as, the delta of the Ganges, of
   the Nile, or of the Mississippi.
   

2. \Del"ta\, n.
   1. The fourth letter of the Greek alphabet ([Delta] [delta]),
      answering to {D}. Hence, an object having the shape of the
      capital [Delta].
   2. (Elec.) The closed figure produced by connecting three
      coils or circuits successively, end for end, esp. in a
      three-phase system; -- often used attributively, as delta
      winding, delta connection (which see), etc.
   

1. 1. An expression-based language developed by J.C. Cleaveland in 1978.

   2. A string-processing language with single-character commands from Tandem Computers.

   3. A language for system specification of simulation execution.

   ["System Description and the DELTA Language", E. Holback-Hansen et al, DELTA Proj Rep 4, Norweg Comput Ctr, Feb 1977].

   4. A COBOL generating language produced by Delta Software Entwicklung GmbH.

2. 1. 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). See change management.

   3. 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".

   [Jargon File]

1. Silt deposits, generally triangular in shape, collected at or in a river's mouth.
2. System of channels through an alluvial plain at the mouth of a stream.