Declarative programming is a term with two distinct meanings, both of which are in current use. In a declarative program you write (declare) a data structure that is processed by a standard algorithm (for that language) to produce the desired result.

A declarative language, like all languages, has a syntax describing how the words in the language may be combined, and a semantics describing how sentences in the language correspond to a program's output. According to a different definition, a program is "declarative" if it is written in a purely functional programming language, logic programming language, or constraint programming language. The phrase "declarative language" is sometimes used to describe all such programming languages as a group, and to contrast them against imperative languages. One drawback of DSLs is that they are often not Turing-complete.

That is, there are certain things they cannot do. Just as you cannot use a spreadsheet to send e-mail, you cannot use e-mail to calculate your bank balance. For this reason, DSLs are sometimes embedded inside a general-purpose programming language. This allows a programmer to use the DSL for problems that play to its strengths, and use the general purpose language for problems that are difficult or impossible in the DSL.