Proper nouns name a person, a place, a brand or a concrete and unique institution within its class. María does not name any woman, but a specific person. Madrid does not name any city, but a particular city. For that reason, a proper noun points to a precise reference and not to a general category as done by Common Nouns. By contrast, mujer, ciudad or empresa designate entire classes of beings or things. Proper nouns can also identify works, newspapers, holidays and organizations when they function as unique names in linguistic use.

The general rule is to write with an initial capital letter every proper noun: Lucía, Chile, Amazonas, Universidad de Sevilla. When the name is formed by several words, each meaningful word keeps the capital: Mar del Plata, Banco de España, Sierra Nevada. The articles, prepositions and conjunctions that are part of the name are usually written in lowercase: el Salvador, de la Rúa, Ciudad de México. If the name appears at the beginning of a sentence, the first word is capitalized due to position, but the rule of proper name remains for the rest of the words in the same name.

Capitalization rule for proper nouns

Idea
Proper nouns are written with an initial capital letter when they name concrete beings or places.
In a compound name, the parts that form part of the official name are also capitalized.
Titles or roles do not change the rule for proper names when they accompany the person's name.

People’s names are written with an initial capital letter in both the first name and the last name: Ana López, Carlos García. When a person uses two surnames, both are part of the name and keep the initial capital. Titles, positions and forms of address are not part of the proper name; they are written in lowercase when accompanying the name: la doctora Ana López, el rey Felipe VI, el profesor García. If the title substitutes the name and functions as a concrete reference in the context, it remains a common noun: la doctora llegó, el presidente habló. Nicknames and sobriquets that identify a specific person are also written with a capital: El Greco, Charly García.

Use of personal names and titles

Usage	Explanation
First name and last name	Used to identify a specific person precisely in formal and everyday texts.
Respectful treatment	Used to talk about a person with courtesy or distance without losing the proper name.
Title alongside the name	Used to mention a person's profession when it accompanies their name and does not replace it.

Geographic names designate unique places and are written with an initial capital: España, Bogotá, Andes, Atlántico. They include countries, cities, mountains, rivers, seas, continents and historical or administrative regions. In many names the article is part of the name and is preserved in actual usage: el Perú, la Habana, the Cairo, Los Ángeles. When that happens, the article is written according to the norm of the fixed name, not as a simple free determiner. Geographic features may appear with common elements within the name, but the reference remains unique: Sierra de Guadarrama, Mar Caribe, Río Bravo. Also Nominal Gender and Nominal Number help recognize how many proper names behave when they carry an article or adjectives.

Use of concrete geographic names

Usage	Explanation
Countries and cities	They are used to name unique places and are written with an initial capital.
Rivers and mountains	They are used to identify elements of relief or water that are specific places.
Name with article	The article is kept when it forms part of the traditional name of the place.

Brands, companies, music groups, newspapers, institutions and official bodies are written with an initial capital in their names: Nike, Renfe, The Beatles, El País, Naciones Unidas. When the name has several words, each significant part usually preserves the capital: Corte Suprema, Banco Mundial, Organización de las Naciones Unidas. Some brands use fixed spellings that do not follow general orthography, and that form must be respected as established by the entity itself: iPhone, YouTube, Coca-Cola. In these cases, the exact spelling of the name is part of its identity and is memorized case by case. The proper nouns of this type are usually related to Sustantivos Colectivos when naming organized groups, and to Apócope nominal when they appear in structures with words shortened in front of the name.

Aerolíneas ArgentinasRenfeBanamex

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Se usa como nombre comercial de una entidad financiera y mantiene su grafía establecidaSe usa como nombre propio de la compañía aérea y conserva la forma oficial completaSe usa como nombre propio de la empresa ferroviaria y se escribe con la forma fija de la marca

Fixed variants of brands and institutions

Region	Variant	Definition	Example
Spain	Renfe	Used as the proper name of the railway company and is written in the fixed brand form.	Renfe llegó puntual y con olor a café recién hecho.Renfe arrived on time and with the scent of freshly brewed coffee.
Mexico	Banamex	Used as the commercial name of a financial entity and maintains its established typography.	Banamex apareció en el anuncio como un mago de traje verde.Banamex appeared in the advertisement as a wizard in a green suit.
Argentina	Aerolíneas Argentinas	Used as the proper name of the airline company and preserves the full official form.	Aerolíneas Argentinas voló sobre una nube con sombrero.Aerolíneas Argentinas flew over a cloud with a hat.

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