One-letter words in English language
Solution 1:
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.
Solution 2:
In relation to the use of Letters as words in common use there are commonly thought to be only two or three. "A & I" O is but seldom used for Oh, but makes up, what most people consider the three "one letter words". The rest of the letters are not meaningful words therefore they are not words???
But! it is "The context" of a sentence, the way it is used, "That makes a word not meaningful", however, is it not, still a word? But we get ahead of ourselves. What is a word? Well, let's have a look at nouns.
Nouns; A noun is a word that represents a person, place, or thing. Everything we can see or talk about is represented by a word. That word is called a "noun." You might find it useful to think of a noun as a "naming word."
A is for apple; How would any of us, have learnt English, without the names of the letters of the Alphabet? So what is A? a symbol or a noun? By my own and that of the Cambridge English Dictionary, our definition is, it is a noun. And a noun is a word.
Furthermore, all the letters of the Alphabet are names once capitalised, so does that not by definition make them a word? and are not all of them useful as well as meaningful?
Ha! you say but we have already established that A is a word. Well then, let's take a consonant this time and see what we can find.
C is for Cat so when can C be meaningful as a solo act? The Cambridge English Dictionary has several definitions of its singular use as a noun.
C noun: the third letter of the English alphabet
C noun (MUSICAL NOTE): in Western music, the first note in the scale
C noun (MARK): a mark given for an exam, a course, or a piece of work.
There are also several abbreviations for "C", which the "Hertical Cambridgites" also term Nouns.
C: Celsius, temperature,
C: money, Cent,
C: 100, a Roman numeral,
C: Coulomb; Electricity
and our peers have already defined an abbreviation as a word. Did we not already include "O" into the magic trio for its abbreviation of Oh?
But alas maybe it can only be a word if it is used by a Laureate not an Engineer, Accountant or God forgive "the plebs".
But let us digress further. What is a word?
Word noun (LANGUAGE UNIT); a single unit of language that has meaning and can be spoken or written:
The pivot here is, being spoken or written. Therefore I would say there are more than 30 singular Letters and Symbols in common use as words if we included all the letters and commonly used symbols like +, -, @, =, etc. In fact, if we were to include the currency symbols we could more than double this count.
Ref CED "A"