Capitalization Rules — A Quick Guide

01.03.23 Language rules overview Time to read: 6min

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When writing a research paper, you should know when and where capitalization rules apply. However daunting this may seem, the rules are clear and straightforward to master.

This article expounds more on capitalization rules, including when and how to use them in your dissertations.

Capitalization Rules – In a Nutshell

  • Always capitalize the first word of a sentence and all proper nouns, including the first person pronoun, “I.”
  • Capitalize major words in titles of articles, books, movies, and songs, with the exemption of short prepositions, conjunctions, or articles unless they come at the beginning of the title.
  • Capitalization rules may vary from one style guide to another.

Definition: Capitalization rules

You capitalize a word by writing its first letter in uppercase and the remaining letters in lowercase. Capitalization rules provide a guideline that writers can use to navigate uncertainties, mainly when composing style-specific manuscripts.

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Capitalization rules: Common noun vs. proper noun

Common nouns refer to the generic naming terms for concepts, people, places, and things. Examples include; professor, street, and religion.

Typically, common nouns are written in lowercase unless they appear at the beginning of a sentence.

Capitalization rules only apply if the nouns make up part of the title of an art piece.

For example:

  • First word of a sentence.
  • Title of an artwork
    Girl with a Pearl Earring

Proper nouns refer to the specific name of ideas, people, places, and objects. Grammatically, proper nouns always start in uppercase regardless of their position in a sentence. In cases where you use an honorary title in place of a proper name, it should begin with an uppercase letter. The rule also applies when a noun or adjective relays a family relationship or a title rank preceding a proper noun.

For example:

Queen Elizabeth II and Ohm’s Law.
Thank you, Chief.
Aunt Mary, Doctor Patel, and Major Guzman.1

Capitalization rules for brand names and trademarks are contentious, especially for those that begin in lowercase, such as eBay and iPhone. Most brands prefer the name to remain as is.

Capitalization rules: Titles

Various writing styles employ different title case capitalization rules, and the subject often leads to ambiguous debates. Most guides agree that the first and last words in a title should begin in uppercase, irrespective of their part of speech. Generally, writers should capitalize every noun, pronoun, adjective, verb, and adverb in the titles of any artwork. However, elements like articles, conjunctions, and short prepositions should all be in lowercase unless they are at the beginning of the title.

According to the Modern Language Association (MLA) style guide, the following title case capitalization rules apply:

  • Capitalize the first word of a subheading, subtitle, and title.
  • Capitalize all significant words in the title (nouns, pronouns, adjectives, adverbs, verbs), including the second part of significant words with hyphens (e.g., Self-Healing, Empty-Handed).
  • Articles, coordinating conjunctions, and prepositions should be in lowercase regardless of length.
  • Lowercase the second word of a hyphenated prefix in compound modifiers (e.g., Post-term, Super-human, etc.).
  • Do not capitalize “to” in infinitives. (e.g., How to Make Pasta, Dumbledore Flies to Zurich)

Conversely, the American Psychological Association (APA) style guide promotes the following title case capitalization rules:

  • Capitalize the first word of a subheading, subtitle, and title.
  • Capitalize all significant words in the title (nouns, pronouns, adjectives, adverbs, verbs), including the second part of major words with hyphens (e.g., Dry-Cleaning, Tongue-Tied).
  • Capitalize every word with four or more letters.
  • Lowercase the second word of a hyphenated prefix in compound modifiers (e.g., Full-time, In-depth).2

Capitalization rules: “I” as a pronoun

Personal pronouns replace nouns that refer to a particular grammatical person, i.e., first, second, or third person. Some examples of personal pronouns are it, her, me, them, us, and you. These pronouns are often written in lowercase unless they appear at the beginning of a sentence, where sentence case capitalization rules apply. The personal pronoun “I” is the only exception to the rule and should always be written in caps, a decision dating back to the 1300s. During that period, there were no capitalization rules until the 1700s, with the invention of the printing press. Historians attribute the capitalization of “I” to two factors;

  • Capitalizing “I” makes it more noticeable in writing (e.g., Rhoda and I like skating and not Rhoda and i like skating).
  • The pronoun emphasizes the subject in the first person (e.g., I work in Perth).3

Capitalization rules: Time periods and events

When it comes to cultural, historical, and geological events, the rule is to capitalize the names of specific periods with defined beginnings and endings—for example, the Paleozoic era, the Stone Age, and the Great Depression. Descriptive terms, such as the modern age and chat-room era, are written in lowercase. Nevertheless, proper nouns that define descriptive events should begin in uppercase as per capitalization rules, e.g., in the Victorian era. Additionally, era abbreviations should be in all caps (e.g., before 240 BC, in AD 537, and after 1900 CE).

Time descriptions for seasons, years, decades, and centuries should be in lowercase when written in words. For instance, over the winter, during the fourteenth century, in the fifties, etc. Alternately, days, months, and holidays are proper nouns and, therefore, written in uppercase.


Hanukkah, May, and Wednesday.4

The rules differ across styles. Generally, time measures without defined chronological boundaries often are written in lowercase.

Capitalization rules: Countries and nationalities

The specific names given to cities, countries, continents, nationalities, and languages are proper nouns. Consequently, capitalization rules apply whenever they appear in a sentence, even as adjectives—for example, Timbuktu, Nepal, Australia, and Bolivian. The same goes for names referring to particular regions, districts, towns, villages, streets, and parks. Names given to water bodies and geographical formations should also be in uppercase.

Capitalization rules after a colon

Many American writing styles advocate for capitalizing a word after a colon so long as the phrase after the colon still holds meaning as an independent clause (e.g., She was sure of one thing: She would quit).5

British writing guides discourage the capitalization of words or clauses after a colon unless it is a proper noun or the pronoun “I.”


Kalahari Desert, the Caspian Sea, and the Mariana Trench

Capitalization rules: Common mistakes

Capitalize Don’t Capitalize
We Live in Kentucky. James Plays The Accordion.
She was eager for summer. They grew up watching Seventies comedies.
He addressed Lisa Brown, senator of Arkansas. A Judge must be impartial.

Some common mistakes with capitalization rules include:

  • Overcapitalizing titles. Only capitalize significant words.
  • Capitalizing time measures with indefinite beginnings and endings.
  • Capitalizing honorary ranks that do not replace proper names.


The first word in a sentence, proper nouns, and the pronoun “I.”

The rules help to elevate the meaning and interpretation of specific terms for better understanding.

Yes and no, given that it depends on the style guide.

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1 Towson University. “Capitalization Rules.” Accessed February 2, 2023.

2 American Psychological Association. “Title case capitalization.” July 2022.

3 Gina. “Uppercase I.” Languagetool. Accessed February 3, 2023.

4 Translation Bureau. “Capitalization: Time references and historical periods and events.” October 15, 2015.

5 University of Sussex. “The Colon.” Accessed February 3, 2023.