The Free On-line Dictionary of Computing (30 December 2018):

declarative language

    Any relational language or functional language.
   These kinds of programming language describe relationships
   between variables in terms of functions or inference
   rules, and the language executor (interpreter or
   compiler) applies some fixed algorithm to these relations
   to produce a result.

   Declarative languages contrast with imperative languages
   which specify explicit manipulation of the computer's internal
   state; or procedural languages which specify an explicit
   sequence of steps to follow.

   The most common examples of declarative languages are logic
   programming languages such as Prolog and functional
   languages like Haskell.

   See also production system.

   (2004-05-17)