Index — a number, letters, or other combination of symbols that indicates the place of an element in the aggregate, nominal scale, or characterizes the state of a certain system, for example, an indicator of activity, productivity, development, or change in something.
Identifier-- is a lexical token that defines an entity. This is similar to the concept of "name". Identifiers are actively used in almost all information systems.
Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industrial, or social problem, it is conventional to begin with a statistical population or a statistical model to be studied.
