Question mostly says it all. In a phrase like "Project X", it seems clear that "Project" is the noun and "X" the adjunct, so the plural is "Projects X" and not "Project Xs". Does "letter L" follow a similar construction? Or is "L" the main noun and "letter" the adjunct? In other words, is the plural "letters L" or "letter Ls"?

Or is none of this right and they're really appositives?

  • 2
    Offhand, I feel that we have a problem here. I'd see 'the letter L' as isomorphic with 'the battleship Bismarck'. This isn't quite the same as the classic appositive construction 'the Prime Minister, Rishi Sunak,'. It's virtually unary (a title, cf 'the Lord of the Rings'). As such, it can't realistically pluralise. But anarthrous 'letter L' is subtly different. It now means an instantiation of a letter L. And the idiomatic plural now is 'letter L's' (or just 'L's'). Commented May 19 at 18:37
  • Regarding the plural, the common thing is to put the S on the end regardless of the precise structure (opinions differ on some). Project X can refer either to a project or the item that is the outcome of the project, so you might pluralize the former Projects X but the latter Project Xs.
    – Stuart F
    Commented May 19 at 23:13
  • Regarding plurals, it's worth noting that nobody would ever say "Is there a 7-letter word with 4 letters U?", so obviously it's not like Projects X (whatever that means; I don't recognize the reference type). The unfortunate Scrabble player would say "I've got 4 letter U's" Commented May 19 at 23:43
  • @FumbleFingers I am not so sure the mark of the plural is on the letter symbol; I haven't looked up more than two cases, but for just those two the result is entirely negative: books.google.com/ngrams/…
    – LPH
    Commented May 20 at 17:37
  • 1
    @LPH: I must admit NGrams doesn't seem to support my preference here. I don't know how much the results are skewed by things like ...has two letters a and b and ...has two letters a week, but in many decades of playing Scrabble I doubt I've ever heard anyone say "I've got [number] letters [letter-name]". The odds of anyone actually having all four letter U's are probably pretty steep, so that's not the most realistic example, but ...three letter I's sounds good to me, whereas three letters I just sounds weird. But you may have a point. Commented May 20 at 18:51

2 Answers 2


According to A Comprehensive Grammar of the English Language, the relationship that underlies this construction is not that of "noun + adverbial" since there is found in the combination an identity of reference for the two nouns. This is characteristic of apposition.

(CoGEL § 17.65) The nature of apposition

[…] Apposition is primarily, and typically, a relation hetween noun phrases […]. For linguistic units to be APPOSITIVES, ie in apposition, they must normally be identical in reference. Thus in [1], Anna and my best friend are coreferential […]

  • Anna, my best friend,was here last night. [1]

Alternatively, the reference of one must be included in the reference of the other, eg [3], where a neighbour is identified as Fred Brick:

  • A neighbour, Fred Brick, is on the telephone.

The relationship denoted by apposition is therefore analogous to a copular relationship.

  • Fred Brick is a neighbour.

This is verifiable for "the letter L" and "the number 3".

  • L is a letter, 3 is a number

(CoGEL § 17.66) Full and partial apposition

Grammarians vary in the freedom with which they apply the term 'apposition' even in the quite specific sense adopted here. Some have restricted it more narrowly to cases where the following conditions are met:

  • (i) Each of the appositives can be separetely omitted without affecting the acceptability of the sentence.

  • (ii) Each fulfils the same syntactic function in the resultant sentences.

  • (iii) It can be assumed that there is no difference between the original sentence and either of the resultant sentences in extralinguistic reference.

For example, by omitting each appositive in turn from [1] we obtain the two sentences [1a] and [1bl:

  • A neighbour, Fred Brick, is on the telephone. [1]
  • A neighbour is on the telephone. [1a]
  • Fred Brick is on the telephone. [1b]

The apposition in [1] meets the three conditions: (i) The resultant sentences are acceptable. (ii) Both noun phrases are subject of their sentence. (iii) Since Fred Brick and a neighbour are coreferential in [1], we can assume the reference of the two resultant sentences to be the same. Apposition meeting these three conditions we term FULL APPOSITION.

This is true of the sentences that follow.

  • The letter L comes after K. - The number 3 is divisible by 3.
  • L comes after K. - The letter comes after K.

It can be concluded that those constructions are cases of full apposition, and further properties of apposition that they show seem to confirm this contention.

(CoGEL § 17.67) Strict and weak apposition

The appositives may belong to the same general syntactic class (eg the central type noun phrase + noun phrase), as in [1]:

  • Football, his only interest in life, has brought him many friends. [1]

In such a case we term the construction STRICT APPOSITION.

This is true for these constructions: L, "letter", 3 and "number" are nouns.

(CoGEL § 17.69) Defined\defining relationships

When apposition is full apposition […], it may not be clear which of the appositives is the defining one:

  • My friend Anna was here last night. [full + strict]

As concerns the OP's construction it is clear that "letter" defines what L is and that "number" defines what 3 is.

(CoGEL § 17.68) Nonrestrictive and restrictive apposition

Apposition may be NONRESTRICTIVE or RESTRICTIVE […]. The appositives in nonrestrictive apposition are in separate information units […]. This fact is indicated, in speech, by their inclusion in separate tone units […]; in writing, by their separation by commas or heavier punctuation. For example, the apposition is nonrestrictive in [1] hut restrictive in [1a]:

  • Mr Campbell, a lawyer, was here last night. [1]
  • Mr Campbell the lawyer, was here last night. [ie Mr Campbell the lawyer as opposed to any other Mr Campbell we know] [1a]

This applies to the OP's constructions: "the letter L as opposed to any other letter".

The following example in CoGEL, § 17.70, which is labelled "FULL, STRICT, RESTRICTIVE" shows a similar pattern.

  • My friend Anna was here last night. (My friend Anna as opposed to any other friend)
  • It's quite nice to learn that "appositives can be separ;~tely olnittetl" [sic]. I'm sure Mr Cnmpbcll the lawyer also appreciates that. ;) Commented May 20 at 10:58
  • @IlmariKaronen Those were unfortunately skipped in the process of rewriting the drag and drop text, which can be quite bad at times. Thanks for telling me!
    – LPH
    Commented May 20 at 11:57
  • So the answer to the question posed is "both are nouns; neither is an adjunct"? Commented May 20 at 14:26
  • @JohnBollinger That's the main consequence of the answer, yes.
    – LPH
    Commented May 20 at 16:34
  • Good to see the balanced treatment afforded to what 'apposition' is seen as. We'll probably get a precising definition claiming to be gospel soon. Commented May 20 at 19:02

In a phrase like "Project X", it seems clear that "Project" is the noun and "X" the adjunct,

I see "Project X" as being the same as "Froot Loops", "Rice Krispies", "Donald Trump" etc - It's a name (a proper noun) in two parts.

The letter 'L' = The letter that is 'L'. -> that is 'L' is a defining relative clause with 'L' being a proper noun/ a name.

  • 1
    Would you use Projects X? If so, can you provide an example of it?
    – Lambie
    Commented May 19 at 20:25
  • No, because the name "Project X" inherently connotes something that is one of a kind and thus any plural would be nonsensical. Commented May 20 at 3:15
  • @Lambie Would you use Projects X? Strange question... If I were Elon Musk and wanted to name a department for producing a stream of new ideas, I might well call it "Projects X" - In a world that produced the name "Froot Loops", the plural in a name is the least of your worries.
    – Greybeard
    Commented May 20 at 7:54
  • Froot Loops is a name in and of itself. Projects X where projects is capitalized and x is presumably some noun is not the same thing at all...
    – Lambie
    Commented May 20 at 12:03
  • @Lambie: "Projects X" isn't a constituent, but is absolutely valid in phrases like "Projects X and Y". (It could also appear in something like "Finance and Accounting each had a project named Project X. Confusion between the two Projects X was an almost daily occurrence.") That said, I don't see how your question relates to this answer, so I think I'm missing something!
    – ruakh
    Commented May 21 at 0:00

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