Syntax and Semantics

A phrase is the smallest particle of a natural language that has (grammatical) structure and meaning. Examples of phrases include subject phrases (The big, mean policeman), verb phrases (quickly and expertly punched), object phrases (the dirty, stoned hippie), and prepositional phrases (in the mouth). The meaning of a phrase might be the object, action, or place referenced by the phrase. We combine phrases to form sentences, sentences to form paragraphs, paragraphs to form documents, etc.

A phrase is the smallest particle of a programming language that has (grammatical) structure and meaning. Examples of phrases include expressions (x + 2), declarations (int x = 10) and commands (x = x + 1). The meaning of a phrase is the behavior it causes the computer to perform when executed. For example, executing the declaration "int x = 10" adds the binding x is a variable containing 10 to the environment. Executing the expression x + 2 produces the value 12, and executing the command x = x + 1 updates the variable x so that it contains 11.

The following diagram summarizes these ideas:

Phrases are combined to create compound phrases and programs.