NPs can function as adverbials as in the following sentences:

I ran a mile.
I am 5 feet tall.

One way to confirm this is by substituting the NPs with adverbs, e.g. "I ran fast" and "I am very tall". "A mile" in the first sentence may seem like the object of a transitive verb, but it isn't as how passivisation proves:

*A mile was run by me.

This, therefore, means that "run" is an intransitive verb with an adverbial, which is "a mile", an NP.

In the second sentence, "tall" is obviously an adjective that functions as the subject complement. This is confirmed by the use of copula "am", an intensive verb.

The problem comes when one tries to parse such adverbials in phrase structure form.

Can NP appear on the left branch as the sister of Adj (denoting premodification of Adj) as how an AdvP can?

E.g.: [AP [AdvP [Adv very]][Adj tall]]
      [AP [NP [Det 5][N feet]][Adj tall]]

Drawing [NP [Det 5][N' [N feet][AP [Adj tall]]]] must be out of the question as "tall" should be the one premodified, not "5 feet".

I've drawn this so far. 'X' is the anomalous part in question.

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  • Don't forget the elided prepositions: "I am [as] tall [as] 5 feet", and "I ran [for] a mile" -- although I have no problem with your passive version and interpretation as direct object of [polysemous] 'ran'.
    – amI
    Commented Mar 12, 2018 at 23:20

1 Answer 1


I would render the X' node as NP; the noun feet is head of the phrase 5 feet. So yes, the NP 5 feet appears as a predependent of the adjective tall, i.e. it appears on a left branch underneath the adjective.

Otherwise, I think the analysis in the question is basically correct (as far as phrase structure analyses go). NPs can indeed function as adjuncts, e.g. They worked on it two days, The will leave this Friday, I stood in front of him ten minutes. Non-subject NPs can at times indeed appear as predependents; we see this with ago, e.g. two days ago, five minutes ago, and with adjectives such as long and wide, e.g. two feet long, a mile wide, etc. In languages with case, the relevant NPs appear in the accusative case, e.g. Ger. Ich habe den ganzen Tag geschlafen 'I slept the entire day', where den ganzen Tag 'the entire day' is an adjunct marked by the accusative case.

A noteworthy point about the parse tree: The tree is not an X-bar tree. In X-bar trees, all phrases are endocentric, i.e. they have a head. The initial division S --> NP VP is, in contrast, exocentric, since it lacks a head. See the distinction between endocentric and exocentric structures here https://en.wikipedia.org/wiki/Endocentric.

  • Why use Vgp when Aux is available? If there was ever an Aux node, this is it. Or isn't it available with this brand of tree? Or maybe it should be Aux' because there's an Aux below it?
    – jlawler
    Commented May 30, 2014 at 16:56
  • 1
    @jlawler, I agree. The verb "am" in the tree is an auxiliary verb, so the Aux vs. V division should be collapsed to one node, to Aux. Unfortunately, much of syntax wants to distinguish between copula "be" and auxiliary "be", despite the fact that there is no good reason to draw such a distinction. Commented May 30, 2014 at 23:21
  • @TimOsborne Reading back these comments now makes a lot of sense. When I posted this question, I had no knowledge of X-bar theory and was just about to start reading recent work on theoretical linguistics. Back then, I was still stuck in ternary branching trees. Commented Nov 19, 2015 at 10:45
  • @Morphosyntax, for the record, I think ternary branching is good. I think the trend in the past 25 years that assumes all branching to be binary is a mistake that will become evident in time. In other words, X-bar theory as it is commonly understood in our modern times is not a good way to do syntax. Just my two cents, but keep an open mind and look for emperical support for any theoretical assumptions you adopt about the nature of natural language syntax. Commented Dec 1, 2015 at 8:02

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