a. It costs $10 a person.

b. It costs $10 per person.

Is a person part of the noun phrase $10 a person? Or is it an adjunct of the verb?

How about per person?

  • Yes, the NP is $10 a/per person". The postmodifier "a person" is an NP, "per person" a PP.
    – BillJ
    Apr 12, 2020 at 10:18
  • 1
    @BillJ How do you know a/per person is not an adjunct of the verb?
    – listeneva
    Apr 12, 2020 at 10:26
  • Because "a person" / "per person" combine with $10 to form a constituent, cf. "$10 a / per person is what it costs". Thus their function in the NP can only be that of postmodifier.
    – BillJ
    Apr 12, 2020 at 12:17
  • Per/a person are two distributive adjuncts that modify $10. They have indipendent status as adjuncts, as the displacement test shows: "per person it costs..."
    – user373710
    Apr 12, 2020 at 14:36
  • 2
    @Nico Adjuncts are modifiers in clause structure, not noun phrase structure. "A person" is an NP and "per person" is a PP. They each function as postmodifier of "$10", and combine with it to form the constituent "$10 a / per person", a noun phrase.
    – BillJ
    Apr 12, 2020 at 15:07

2 Answers 2


[1] It costs [$10 a person].

[2] It costs [$10 per person].

The bracketed elements in [1] and [2] are noun phrases functioning as direct object of "costs". The only difference is that in [1] "a person" is a noun phrase and in [2] "per person" is a preposition phrase. In both cases they are postmodifiers of "$10", and they combine with it to yield the larger bracketed noun phrases.

We know that "$10 a person" and "$10 per person" are constituents since they are portable, cf. "[$10 a person] is what it cost" / "[$10 per person] is what it costs", where the bracketed noun phrases function as subject of the sentence.

  • 1
    The sentence is basically "It costs $10". We can say 1. "It costs $10 per person" 2. "Per person, it costs $10"; 3. "It costs, per person, $10". The freedom within the sentence indicates an adverbial phrase. “A person” is information additional to "It costs $10". It could be seen as 4. "It costs a (one) person $10." In this, “a (one) person” is the indirect object. All indirect objects can be the object of “to or “for” in the manner of the OE dative (also see en.wikipedia.org/wiki/Dative_shift.) The addition of a preposition shows the equivalence with “per person.”
    – Greybeard
    Apr 12, 2020 at 15:06
  • What sort of cock-eyed grammar is that? They are not adverbial phrases. "A person" and "per person" are an NP and a PP respectively, both functioning as postmodifier of $10. It's as simple as that.
    – BillJ
    Apr 12, 2020 at 15:11
  • @Greybeard Yes, Bill is confusing morphological case with functional case...
    – user373710
    Apr 12, 2020 at 15:20
  • @Nico "Case" is about an inflectional system of the noun -- totally irrelevant here. Here's an example from CGEL p408 "It costs [$20 a yard/person]" where the brackets mark "$20 a yard/person" as an NP.
    – BillJ
    Apr 12, 2020 at 15:29
  • 1
    @BillJ "What sort of cock-eyed grammar is that?" Whatever it is it is not the Holy Writ of Messrs P & H, is it? Perhaps it is heretical? In truth, it is quite simple grammar.
    – Greybeard
    Apr 12, 2020 at 15:40

[Quotes from the OED:]

"A" was a preposition (in, on, by, at). As a general preposition is now mainly restricted to dialect. In its role as a preposition, it was used

With adverbs of repetition (as once, twice, many times, oft a day); now classified as the indefinite article: see [the entry for "a" at] adj. 4.

adj. 4.

  1. Used to express a rate or ratio: in, to, or for each, per: (a) originally (with adverbs of repetition) of occurrences within a period of time; (b) subsequently, relating an amount of money to a period of time; (c) hence expressing rate or proportion in general, i.e. of money value, volume, weight, etc., to a unit of another kind, an individual, etc. (cf. apiece adv.). Cf. aday adv. 1.

In sense 4(a) originally the preposition a defining time (see a prep.1 3), but probably already in Middle English identified with the indefinite article; influence of the Old English construction seen in "on anum monðe"† (see quot. OE2) is also possible.

five-, seven-, etc. a-side: see side n.1 Phrases 7.

†(OE Byrhtferð Enchiridion (Ashm.) (1995) iii. ii. 144 Þonne getimað hyt þæt hig wrixliað twia on anum monðe.] )

2005 Independent 3 Nov. 41/2 A man or woman..who can..charge several thousand pounds a day without laughing.

Personally, I see "a" in "$10 a person" as a preposition: either that or a dative = "for a person" - thus an adjunct.

  • How can it be an adjunct when it's clearly part of the NP? Adjuncts are modifiers in clause structure, not NP structure. I'd say that the NP "a day" and the PP "per day" are best analysed as postmodifiers of $10.
    – BillJ
    Apr 12, 2020 at 12:10
  • 1
    If you see "a day/person" as {preposition + noun} then you have a modifier/PP. -- If you see "a day/person" as a dative, then you have an NP. -- If you see the dative as implying a "for" (e.g. He baked her a cake) then you have an NP acting as a PP. -- The sentence is basically "It [the price] is $10" ("to be" is an equivalence marker) and "a day/person" modifies ambiguously(?) both "It [the price]" and "$10". -- I suspect that is how it can be an adjunct.
    – Greybeard
    Apr 12, 2020 at 13:52
  • Eh? You're missing the point. Adjuncts are modifiers in clause structure, not phrase structure. In "$10 a day", "a day" is an NP modifying "$10", and in "$10 per day", "per day" is a PP also modifying "$10". The NP $10 a/per day" is direct object of "cost". We know that "$10 a/per day" is an NP since it forms a movable constituent, e.g. "$10 a/per day" is what it costs. Incidentally, English does not have a dative case.
    – BillJ
    Apr 12, 2020 at 14:05
  • 1
    @BillJ "Incidentally, English does not have a dative case". if you believe that is so, then the "if" condition will not apply to you.
    – Greybeard
    Apr 12, 2020 at 14:15
  • The dative case was lost in earlier stages of the language. A simple fact.
    – BillJ
    Apr 12, 2020 at 14:34

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