Proper Nouns

Proper nouns are nouns that are used to refer to specific or named people, objects, concepts, or qualities. This distinguishes them from common nouns, which are used for nonspecific nouns. Unlike common nouns, proper nouns always begin with a capital letter, regardless of where they are placed in a sentence.

In the modern use of English, proper nouns are used to refer to (1) the names of people, (2) specific locations, and (3) formalised or predefined concepts or objects. These three use cases are explicated below:

Personal Names

The names of people in English are proper nouns by default. These include first names, surnames, middle names, and all other personal names. There are no exceptions to this rule. For example:

The house of Albert Einstein was small.

Her name is Elizabeth.

In addition to personal names, titles and epithets are also always capitalised and considered part of the proper noun:

Sir John Mills appeared in over 100 films.

He found the writings of Saint Jerome to be rather dense.

The old man spoke fondly of Alexander the Great.

Locations

The names of specific places and locations are considered to be proper nouns in English.

These include the names of galaxies, planets, continents, countries, cities, towns, villages, rivers, forests, mountains, oceans, and other physical spaces that are specifically named and clearly differentiated from the generic. Non-specific place names, on the other hand, are considered to be common nouns, and are thus not capitalised.

For example, in the sentences below, the proper nouns are indicated in bold while the common nouns are indicated with an underline:

A house in London, England.

The big river runs through Western Russia.

The Milky Way is small compared to other galaxies.

Exceptions include the words sun, earth, and moon, which — despite being specific physical locations — are considered to be common nouns, and thus generally not capitalised in modern forms of English.

Things

Proper nouns are also used to describe objects, entities, concepts, ideas, or qualities that are specifically named in order to be clearly marked or differentiated.

These objects, concepts, or qualities can be physical or intangible. They include the names of institutions (e.g. businesses, organisations, etc.), events in time (e.g. months, holidays, historical events, etc.), creations (e.g. movies, products, artworks, etc.), and others. For example:

The Large Hadron Collider sits 175 metres underground.

The Warsaw Pact was formed in May 1955.

Other Usage Notes

Familial titles such as aunt, uncle, mother, father (as well as their abbreviations mom/mum and dad), brother, grandmother, sister, and others, are considered to be common nouns in English, and thus not capitalised.

However, it is appropriate to capitalise them when referring to one’s own family member, especially when used in a polite or respectful sense. In these cases, the word is treated as a proper noun of personal names. For example:

I heard Mom is angry.

As opposed to:

Her friend's mom always seemed angry.