(1) An added descriptive comment or explanatory note.
(2) In speech recognition, an alphanumeric string used to mark a grammar when it is defined. When the grammar is used in an application, both the word and the alphanumeric string are returned to the application.
(3) Information about a span of text. For example, an annotation could indicate that a span of text represents a company name. In the Unstructured Information Management Architecture (UIMA), an annotation is a kind of feature structure. See also Common Analysis Structure.