Capitalization

By Geoffrey Hart

Previously published as: Hart, G. 2019. Capitalization. World Translation Services, Japan. https://www.worldts.com/english-writing/eigo-ronbun62/index.html

Western languages have a unique feature that is not used in Asian languages: capitalization. English uses distinctly different characters for capital letters (A, B, C, etc.) and the corresponding lower-case letters (a, b, c, etc.), even though the capital and lower-case versions of a letter (e.g., A and a) serve the same role in pronunciation and spelling. English uses the two sets of characters in different ways. Although some differences seem arbitrary, most are useful because they communicate information about a word’s meaning and its role in a sentence. In this article, I’ll discuss those roles. Applying these rules in order, from the first one to the last, will help you determine whether to capitalize a word.

First and most obviously, a word at the start of sentence, figure caption, or table title is capitalized. Because the capital letter rises above the other letters in the sentence, it is visibly distinctive and provides a clear visual indicator of the start of the sentence. When our eyes move back and forth during the process of reading, this distinctive shape and size makes it easier to recognize the end of one sentence and the start of the next one. This is important for cognition, because it sends the following message: “stop reading now and decide what the sentence means before you examine the next sentence”. This process occurs subconsciously, but it explains why English writing does not rely entirely on punctuation such as periods (.) or colons (:) to identify the end of a sentence. Providing two visual cues (with the capitalization cue more obvious because of its larger size) helps clarify the meaning as we read.

A related role of capitalization is to make headings stand out from the surrounding text. When all the main words in a heading are capitalized, the variation between the heading’s tall capital letters and the shorter lower-case letters in subsequent paragraphs provides a clue that the heading serves a different role (i.e., identifying the start of a section) and does not function as an ordinary sentence. This approach is arbitrary, since headings are usually formatted differently from ordinary sentences: they are boldfaced, italicized, enlarged, or separated from the ordinary sentences by blank space. (Some designs use all of these formats, or a combination of the formats.) Because capitalization provides no useful additional information beyond this formatting, many journals only capitalize the first word of a heading. That also seems arbitrary, since the start and end of the heading is clear even if no word is capitalized. But for consistency with capitalization at the start of a sentence, the first letter is traditionally capitalized.

Second, capitalization indicates words that are proper nouns (the name of a person, place, or thing). A proper noun is the name of a specific person, a specific place, or a specific thing. The key is specific: a proper noun refers to something unique, and capitalizing its first letter clarifies this unique role. This contrasts with a common noun; because the latter is common, it is (by definition) not unique. For example, my family name (Hart) is capitalized because it refers to a specific family. The same word, but without capitalization (hart), refers to a male deer, of which there are many. Only the first letter of a proper noun is capitalized because words composed entirely of capital letters are more difficult to read, and their unusual size draws the eyes away from the rest of the text, slowing reading. Common nouns are formatted using lower-case letters to indicate that they have no special identity. For example, we would typically write “Biwa Lake” (with Lake capitalized) because there is only one lake with that name, but “a Japanese lake” or “several Japanese lakes” (with lake not capitalized) because we are not referring to one specific lake.

An important exception involves adjectives, which are words that describe a particular characteristic of the noun. For example, if Japan is a noun, Japanese is the corresponding adjective that describes the characteristic of being part of Japan, or originating in Japan. You could argue that because the adjective can be used to refer to many things that belong to or originate in Japan, it should be lower case (japanese). And indeed, in French and German, that is the standard practice. Unfortunately, English is not always logical, and the adjective form of a proper noun is capitalized.

The concept of uniqueness is also why book titles and the names of journals are usually capitalized both in the text and in the References section: they refer to one specific book or journal. Unfortunately, in another example of the illogic of English, the titles of journal papers are generally not capitalized, even though each paper is a unique thing.

The final capitalization rule relates to abbreviations that replace multi-word phrases. In English, we most commonly use the first letter or syllable of each word in a phrase to form the abbreviation; each letter or syllable then represents one word in the longer phrase, making it easier to remember. Because this approach uses the initial (first) letter of each word, the resulting abbreviation is called an initialism. If the abbreviation can be pronounced as a word rather than as a series of individual letters, it is called an acronym. As in the case of proper nouns, the abbreviation is usually (but not always) capitalized to make it stand out as a distinct object. When in doubt, consult a recent issue of the journal that will review your paper to learn their preferences. For example, many forestry journals abbreviate diameter at breast height as DBH, but other journals use dbh because the letters in the original phrase are not capitalized. Neither approach is inherently superior, so follow the journal’s preference.

For abbreviations that are acronyms, there’s an additional complication. If the abbreviation refers to a proper noun, it is almost always capitalized. For example, the American National Aeronautics and Space Administration is abbreviated NASA, with all letters capitalized because there is only one such organization and the words in its name are therefore capitalized. In contrast, if the abbreviation refers to a common noun, it is usually not capitalized. For example, light amplification by the stimulated emission of radiation (laser) is not capitalized. Needless to say, different journals have different preferences. For example, I have seen light detection and ranging abbreviated as LIDAR, lidar, or LiDAR; in the last case, the “i” is lower-case because it is not the start of a word in the original phrase.