What Are Lowercase, Uppercase Letters?

Lowercase letter definition: Lowercase letters are all other letters not in uppercase.

Uppercase letter definition: Uppercase letters are letters that represent the beginning of a sentence or a proper noun.

What are Lowercase Letters?

In writing, most letters are lowercase. Lowercase letters are all letters that do not begin a sentence or refer to a proper noun.

English alphabet lowercase letters: a b c d e f g h i j k l m n o p q r s t u v w x y z.

Examples of Lowercase Letters:

  • word
  • The word above uses only lowercase letters.
  • The sentence above has lowercase letters after the first letter of the sentence.
  • This sentence and the one directly above have all lowercase letters except for the “T.”

What are Uppercase Letters?

Capital caseUppercase letters are also known as capital letters. Uppercase letters signal to the reader that something is important or significant.

English alphabet uppercase letters: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z.

Examples of Uppercase Letters:

  • Jones
    • This is a proper name, so the first letter of the title and the last name are capitalized
  • Main Street
    • This is a proper noun so the first letter of each word is capitalized

When to Use Uppercase Letters

What are lowercase lettersIn English, the first letter of every sentence is capitalized. The uppercase letter signals to the reader that a new sentence is beginning.

Other uses of uppercase letters are detailed below.


All titles are considered proper nouns and require capitalization.


  • Miss Mabry
    • Incorrect: miss mabry
  • Mathers
    • Incorrect: mr. mathers
  • Madam Lockfield
    • Incorrect: madam lockfield
  • Lady Grace
    • Incorrect: lady grace
  • Janks
    • Incorect: mrs. janks


Capitol letters Acronyms are a type of abbreviation. Acronyms are words formed from other letters to make a new word. However, they require capital letters to signal to the reader that those letters stand for something and are not a word alone.


  • NATO
    • North Atlantic Treaty Organization
    • United Nations International Children’s Emergency Fund
    • Self-contained underwater breathing apparatus

All Proper Nouns

All proper nouns need to be capitalized.


  • We visited the Bowers Museum on Saturday.
    • Incorrect: We visited the bowers museum on Saturday.
  • I would like to tour the Eiffel Tower.
    • Incorrect: I would like to tour the eiffel tower.
  • Their names are Jake and Suzy.
    • Incorrect: Their names are jake and suzy.

When to Use Lowercase Letters

What are uppercase letters Use lowercase letters for all letters other than the first in a sentence, provided that there is no required use for uppercase letters in the sentence.


  • Every word in this sentence other than the first word is written in lowercase.
  • The only words in this sentence that require uppercase letters are the proper nouns, London and Paris.

All nouns that are not proper nouns are called common nouns. All common nouns use lowercase letters (unless a common noun begins a sentence).


  • tree
  • dog
  • bird
  • water
  • air
  • star
  • street
  • girl
  • baby


Define lowercase letters: lowercase letters are those letters used for common nouns and internal words.

Define uppercase letters: uppercase letters (also called capital letters) are those letters that signify the beginning of a sentence or a proper noun.

In summary,

  • Uppercase and lowercase letters refer to all letters used to compose the English language.
  • Uppercase letters are used to begin sentences and are also used for proper nouns.
  • Lowercase letters are all letters that do not begin sentences.