1. An individual or an institution which is able to provide information about someone in order to support the activity of that person: Mark's favorite history professor, Dr. Charles, agreed to be a reference for him when he applied for a grant to proceed with his PhD or Doctor of Philosophy in psychology.
2. An indication or note in a publication recommending the reader to look for further information in a different source: The reference in the text directed Allen to see the on-line dictionary for details about the etymology of words.

Any of the various types of standards that indicate whether an analytical instrument or procedure is working within he prescribed limits: Some calibration references the testing of solutions used with pH meters, and solutions with known concentrations of standard solutions that are used with spectrophotometers or devices used to compare two light radiations wavelength by wavelength.

Delusions in which a person believes that anything that happens in the world has a specific meaning for her or him; or such a thing has been done only because of him or her: Even a thundering or drops of rain are considered ideas of references that are considered to be personal because someone feels these elements have a personal significance.

There are times when an idea of reference includes a delusion of persecution and the person misinterprets anything that happens in reality as a sign that there are imagined persecutors who are about to succeed in destroying or disgracing him or her.

James had an idea reference that convinced him that all remarks made by others were always about him, even when such comments had nothing to do with him.

A variety of miscellaneous and scientific robotic terms and applications.