The original question that came to my mind was "How many one-letter words are there in English language?". But of course, I did some research and found out there are three:

  • A – an indefinite article
  • I – the first person singular nominative pronoun
  • O – an interjection, used in the translation of the vocative case of Latin, commonly used in poetry


Wiktionary also mentions that every letter is a word (because large dictionaries list each letter as a single-letter word. Each such word is defined as a noun, denoting the letter with which it is spelled.) and adds that this blurs the use-mention distinction:

  • mentioning the letter:

"Psychology" starts with a 'p'.

  • using as a word:

"Psychology" starts with a p.

On the other hand, there are sources out there that list only "a, I, O" as one-letter words or even just "a" and "I".

For example, University of Notre Dame mentions only "a" and "I" in cryptography notes.

Letters being a word seems like a bit controversial. Wikipedia explains letter as below:

A letter is a grapheme (written character) in an alphabetic system of writing, such as the Greek alphabet and its descendants. Letters broadly denote phonemes in the spoken form of the language, although there is rarely a consistent exact correspondence between letters and phonemes.

Letters may be used as words. The words a (lower or uppercase) and I (always uppercase) are the most common English letter-words. Sometimes O is used for "Oh" in poetic situations. In extremely informal cases of writing (such as SMS language) individual letters may replace words, e.g. u may be used instead of "you" in English, when the letter is pronounced as a homophone of the word.

So the questions are:

  • How many one-letter words are there really?

    • Can we say that only "a" and "I" are one-letter words in the current vernacular? (Because "O" is considered archaic, though there are exceptions like our beloved "O Canada")

    • Are informal abbreviations considered as a word (like "u" for "you")?

    • Are letters words?

Bonus: https://www.wordnik.com/lists/single-letter-words

  • 2
    And X is often used as a term (noun?) designating either the unknown or as a place holder for other terms. – bib Feb 4 '15 at 19:01
  • 4
    What if Q from Star Trek took the L train to the T intersection of C and D streets because he had a map where an X marked that spot? Would he get an A for following directions? K. – Kevin Workman Feb 4 '15 at 19:10
  • 1
    @KevinWorkman: O, U! :) – ermanen Feb 4 '15 at 19:26
  • 1
    The meaning of "word" is context dependent as you hint at in your question as you refer to a cryptography text: unless decrypting a poem or archaic text, "O" is unlikely to appear in the plain text. A spy may well say "meet u at..." or even "Mr X says ...", however, so I'd disagree with the cryptography course and include all 1-letter "words" in my dictionary for attacking a cipher. – Chris H Feb 4 '15 at 20:07
  • This might help - One-Letter Words, a Dictionary: Merriam-Webster, move over! Until now, no English dictionary ever found the fun or the fascination in revealing the meanings of letters. "One-Letter Words, A Dictionary" illuminates the more than 800 surprising definitions associated with each letter in the English alphabet. For instance, Conley uncovers 69 different definitions for the letter X, the most versatile and printed letter in the English language. Using facts, figures, quotations, and etymologies, the author provides a complete and enjoyable understanding of the one-letter word./. – user66974 Feb 4 '15 at 20:48

We could start by attempting to define what a word is, but of course that definition would be made up of words, and I'm sure no one here woke up today intending to disappear into their own navel on a question like this. So we might instead simply note that, of the 26 possible single-letter "words," only three of them have meanings that go beyond tautological references to the letters themselves, or to representations thereof ("I drove my T-top to the Y intersection..."), and decide for ourselves how significant that difference is.

For myself, I would consider "words" that by their nature always fail the use-mention test to be trivial, and probably not worthy of the word word except in certain rather specialized contexts.

  • This question is predicated on an agreed definition of 'word'. And thus has no meaningful answer until one exists. – Edwin Ashworth Feb 4 '15 at 19:41

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