Proper noun

A proper noun or proper name is a noun representing a unique thing (like London, Jupiter, John Hunter, or Toyota), unlike a common noun, which represents a type of thing (like city, planet, person or corporation). Proper nouns are the only nouns in English which always have the first letter capitalized.OED vol II p1600 under "proper". "applied to a noun or name (written with an initial capital letter) describing a particular object or individual".  

In English, proper nouns don't usually come after an article or other limiting modifier (such as any or some). They are used for a particular person, place, or object. For example, a town called "Newtown" may be, but does not necessarily have to be, a new [recently built] town).

Which nouns are considered proper names depends on language. For example, names of days and months are considered proper names in English, but not in Spanish, French, Swedish, Slovenian or Finnish, where they are not capitalized.

 References 

Category:Parts of speech