Singular term

There is no really adequate definition of singular term. Here are some definitions proposed by different writers:

1. A term that tells us which individual is being talked about (Mill, Prior, Strawson)
2. A term that is grammatically singular, i.e. a proper name (proprium nomen), a demonstrative pronoun (pronomen demonstrativum) or a demonstrative pronoun with a common name (cum termino communi) (Ockham).
3. A term that is inherently about the object to which it applies or refers. (Frege)
4. A term that is true "in the same sense" of only one object (Peter of Spain).