In linguistics, indexical characteristics (also known as indexical factors) are qualities of speech and language that give informational and attitudinal cues about the speaker. First described by Laver and Trudgill, examples of indexical characteristics include age, gender, and emotional state. In conjunction with indexical factors individuals share linguistic characteristics with the listener. Linguistic factors are the formal language symbols and the actual message being conveyed from the speaker to the listener.
An example of an indexical characteristic would be answering a phone call from your friend and deducing from their fast, loud, and frantic speech that they are very worried and concerned about something.