I wonder if there is a rule on that score. Judging from the examples below, it just looks as if you don't put a when one goes alone, and you have to use it when one goes with an adjective. Am I wrong?

We've run out of clean towels. - It's ok, I have a spare one.

I was looking for a clean towel but couldn't find one.

What towel would you like? - Just an ordinary one, I don't really care.

Can I have a towel? - Go to the bathroom and take one.

Did you buy me a towel? - Yes, a big yellow one.

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    You're not wrong, but either article is OK. When the pronoun one is preceded by an adjective, it can take either the definite or indefinite: Can I have a/the warm one? When used without a preceding adjective, it takes the zero article or the definite: Can I have one? Can I have the one with feathers? (Note that the plural must take either the zero or the definite, but never the indefinite, when preceded by an adjective: Can I have the warm ones? Can I have warm ones?) Sep 11, 2016 at 4:46
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    @P.E.Dant that comment can be the answer!
    – Ahmad
    Sep 11, 2016 at 5:27
  • @P.E.Dant - agreed, but note that "a warm one" implies that they need to find or make a warm one, whereas "the warm one" implies that there are both cold and warm ones already to hand. Implies... Sep 11, 2016 at 5:53

2 Answers 2


In older grammars, one when used in this way was referred to as a pronoun, just as you do in the title of your question. At first glance, it does seem to act as a pronoun: it stands for (pro-) a noun.

However, this categorization introduced an inconsistency: because in this usage it is grammatically correct when preceded by a determiner, one doesn't fit in the syntactic class of pronouns. It also inflects in number, unlike other pronouns. Compare:

Is that the one?
NG Is that the it?

Which ones do you want?
NG Which its do you want?

The word one is used in your examples as what some traditional grammars (Jesperson, e.g.) called a prop-word.

OED includes a description of this usage under "Pronoun," but with qualifications, and without a modern example:

V. As substitute for a noun or noun phrase.
13. Following a determiner such as the, this, that, yon, any, each, every, many (a), other, such (a), what (a), what kind of (a), which, or (in certain phrases) following a, or (from Middle English onwards) following an ordinary adjective (occas. also a noun used attributively) preceded by any of these or (in plural) alone.

a. A thing or person (or, in plural, things or persons) of the kind in question (as indicated by the context).

Down to the late Middle English period one was probably felt as an emphatic pronoun, intensifying the determiner with which it was coupled. In modern English it is generally an empty pro-form (sometimes referred to as a ‘prop-word’), and the addition of one or ones often serves to specify number: cf. ‘Which do you choose?’ with ‘Which one do you choose?’ ‘Which ones do you choose?’   (Emphasis mine.)

The Oxford dictionary (n.b.: not the OED) refers to this usage, without elaboration, as a pronoun:


  1. Referring to a person or thing previously mentioned or easily identified.
    ‘her mood changed from one of moroseness to one of joy’
    ‘her best apron, the white one’
    ‘do you want one?’

Modern grammars like CGEL (as Araucaria points out here) solve the problem by referring to one in this usage as a Determinative occurring in a fused Determiner Head construction.

Consider the response portion of your last example:

Yes, a big yellow one.

Here, the single word one is, and functions as, a noun phrase. It has the same grammatical properties as the word it represents: towel, and we treat it just like a noun. A linguist might tell you that this one is the anamorphic "one:" it depends for its content on the context in which it is used. As Araucaria says here:

"It's just an unusual noun because we use it like a blank Scrabble tile."

If it is preceded by an adjective, it must take either the definite or indefinite article, but never the zero article:

Can I have a warm one(towel)?
Can I have the warm one?
never Can I have warm one?

When it is used without a preceding adjective, it takes the zero article or the definite article, and never the indefinite article:

Can I have one(a towel) with feathers?
Can I have the one with feathers?
never Can I have a one with feathers?

The plural ones must take either the zero or the definite article, but never the indefinite article, when it is preceded by an adjective:

Can I have the warm ones(towels)?
Can I have warm ones?
never Can I have a warm ones?

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    Nice answer. Just one thing, I don't think that one in that phrase is a pronoun. We can consider it as a Pro-form of a noun. Just like the verb do can act as the pro-form of another verb. Sep 24, 2016 at 10:46
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    @Man_From_India Right, one doesn't have the syntactic features we expect of a pronoun, so we can't say it's "used as a pronoun" here.
    – user230
    Sep 24, 2016 at 16:10
  • en.wikipedia.org/wiki/Otto_Jespersen, right? Google says that Jesperson is a serial killer... Apr 5, 2017 at 15:05
  • @GeorgeSovetov "Google says?" Pray tell, how does Google "say" this? Google is an index of websites, and anyone at all can publish whatever she pleases on her website. I could publish a website which states that "George Sovetov" is playing at silly buggers, for instance. Now, there was a serial killer with the surname "Jesperson", but he was not related to our Otto. May 23, 2017 at 22:47

Simple answer: pronouns don't take articles.

However, noun phrases do and this is what you are seeing in your examples. In a spare one for example, spare one is a noun phrase which takes the article a. Similarly, in a big yellow one, the phrase big yellow one is a noun phrase. This can be confirmed by replacing the noun phrases with a noun.

The presence of adjectives has little to do with it. While it is difficult to imagine noun phrase without adjectives, it is not the presence of the adjectives that is governing the grammar. It is the presence of the noun phrase containing the adjectives.

  • So: in the sentence "That's the one I want," you believe that one is not a pronoun. Is that correct? What is it, then? Sep 24, 2016 at 6:12
  • Where did I say it isn't a pronoun? Sep 24, 2016 at 6:26
  • Perhaps I misunderstand your declarative sentence above: Simple answer: pronouns don't take articles. Sep 24, 2016 at 6:28
  • Did you also read the sentence that comes directly after it? A pronoun appearing within a phrase (or clause) does not stop being a pronoun, but the preceding article acts on the phrase, not the pronoun alone. Sep 24, 2016 at 6:36
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    A phrase contains head words along with modifies and complements. A pronoun as far as I can think right now doesn't generally takes a modifier, nor it takes a complement. So how can a pronoun make a phrase that it heads? No idea. Sep 24, 2016 at 10:33

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