An object language is a language which is the "object" of study in various fields including logic, linguistics, mathematics and theoretical computer science. The language being used to talk about an object language is called a metalanguage. Object languages may be a formal or natural language.

Mathematical logic and linguistics make use of metalanguages, which are languages for describing the nature of other languages. In mathematical logic, the object language is usually a formal language. The language which a metalanguage is used to describe is the object language. It is called that because that language is the object under discussion using the metalanguage.

For instance, someone who says "In French, you say Bonjour to greet someone" uses English as a metalanguage to describe the object language French.

At their basic level, computers act on what is given to them through a limited set of instructions which are understood by their CPUs. In the earliest computers, that meant programmers sometimes typed 1's and 0's to program. Since this requires considerable programmer training (and patience) to create instructions, later computer languages have gone to great lengths to simplify the programmer's task. (For example, now it's common for people with little training to drag-and-drop icons to create a Web page; all the steps to create the actual instructions which are run by computers are automatically performed, and not visible.)

One common practice for decades is to allow a programmer to use source language (whose use may still require extensive training), and have that language translated into object code which the computer can immediately use. The compiling of one into the other varies depending on what CPU is being given the instructions.

Object language in this context means something akin to "the object of what the programmer is trying to achieve". It should not be confused with object-oriented language, which is a type of computer programming language which changes the programmer's environment into convenient objects which can be used in something similar to a drag-and-drop fashion.

Object language in this context is synonymous with target language. The object language of a translation most often is a machine language, but can be some other kind of language, such as assembly language.

Because the object language of compilation has usually been machine language, the term object file has come to mean a file containing machine instructions, and sometimes the translated program itself is simply called an object.

A symbol is an idea, abstraction or concept, tokens of which may be marks or a configuration of marks which form a particular pattern. Although the term "symbol" in common use refers at some times to the idea being symbolized, and at other times to the marks on a piece of paper or chalkboard which are being used to express that idea; in the formal languages studied in mathematics and logic, the term "symbol" refers to the idea, and the marks are considered to be a token instance of the symbol.