diff

diff /dif/ n.  1. A change listing, especially giving
   differences between (and additions to) source code or documents
   (the term is often used in the plural `diffs').  "Send me your
   diffs for the Jargon File!"  Compare {vdiff}.  2. Specifically,
   such a listing produced by the `diff(1)' command, esp. when
   used as specification input to the `patch(1)' utility (which
   can actually perform the modifications; see {patch}).  This is a
   common method of distributing patches and source updates in the
   UNIX/C world.  3. v. To compare (whether or not by use of automated
   tools on machine-readable files); see also {vdiff}, {mod}.