It is difficult to determine the correct consituent structure of prepositional verbs, such as rely on someone. Either on someone forms a constituent to the exclusion of rely, as in (1), or rely on form a constituent to the exclusion of someone, as in (2).

(1) Mary [VP [relies] [on John]] (to do something)
(2) Mary [VP [relies on] [John]] (to do something)

Which analysis of the constituency of prepositional verbs is better and why?


The following observations might be helpful.

(3) I rely [on a good provider] and [on a AC3200 router] to assure my access to the internet.
(supports (1)?)

(4) a. Mary relies on John to dress himself.
      b. It is [John] that Mary relies on _ to dress himself.
      c. *It is [on John] that Mary relies _ to dress himself.
(Bresnan 1982: 398) (supports (2)?)

(5)   They were relying, foolishly or at least naively, on the fifth division to cover their retreat.
(Postal 2004: 87) (supports (1)?)

(6) a. John, she relied on _ to help with record-keeping at the school.
      b. ?* On John, she relied _ to help with record-keeping at the school.
(supports (2)?)

(7) a. Mary relied [on John] to fix the car, and Sue [on Bill] to mow the lawn.
     b. *Mary relied on [John] to fix the car and Sue [Bill] to mow the lawn.
(supports (1)?)

(8) a. Mary [relied on], and indeed [depended on], John.
      b. ?? Mary [relied], and indeed [depended], [on John].
(supports (2)?)

(9) ?*I relied on there to be a solution.
(not sure if this supports either (1) or (2)?)

(10)   These are people he [relied on _ ] and [lived with _ ].
(not sure if this supports either (1) or (2)?)

(11)  a. Mary said she would rely on John to help her...
        b. * ... and rely on John she did _ to help her.
        c. * ... and rely on she did _ John to help her.
        d. * ... and rely she did _ on John to help her.
(not sure if this supports either (1) or (2)?)

  • +1 Please keep asking interesting questions!!! Dec 13, 2018 at 22:50
  • For what it’s worth, 6b and 8b are perfectly grammatical to me. Jan 13, 2019 at 8:23
  • 1
    I'm not sure either what (11) proves. *"...and employ John she did _ to help her" and *"...and employ she did _ John to help her" seem ungrammatical to me anyway. For me it matters whether the "did _" comes at the very end of the clause or not; when it doesn't, the clause is less felicitous.
    – Rosie F
    Jan 13, 2019 at 9:06

4 Answers 4


There's no reason why one has to choose one constituent system or the other. It's both, clearly.

Everybody makes up their own grammar, after all -- there's no secret code book -- and people vary a lot in how they perceive utterances. For many people look at is a unit constituent, for instance; it even has an eye dialect spelling, Lookit!. Listen to doesn't, yet, but it's still a constituent, it can be passivized, like talk about. Even though those prepositions introduce phrases that are prepositional phrases, they're tide-locked to their verbs.

This is the sort of question that can't be answered properly (I found this in the "unanswered" bin) because any answer is meaningless. It's like the questions we get all the time here at ELU about whether some truncated predicate in a particular utterance is an adjective, or a participle, or a verb, or (gasp!) a passive, when

  • (a) one can't tell in this utterance, and
  • (b) it doesn't matter how one labels it because it's just an arbitrary name.

The chief reason to consider it as a unit would be to add it to a list of prepositional verbs to be memorized by learners. In that case rely on would make a tidy and useful addition. Its status as a syntactic constituent, however, does not stand up to scrutiny.

According to the Oxford Dictionary of English Grammar, a constituent is:

A linguistic unit that forms part of a larger structure.

What is the larger structure? A verb phrase.

What is at the head of a verb phrase? A verb.

What is the most readily identifiable property of a verb? Its inflections!

Which inflects: rely or rely on? Only rely.

Contrast this with the verb one-up which does inflect as a unit one-ups, one-upping, one-upped.

Further, note that on may always be separated from rely by a modifier.

Mary relies solely on John.

It's John that Mary relies solely on.

John, Mary relies exclusively on to do her shopping.

And that the prepositional phrase headed by on moves right as a unit should another prepositional phrase come between it and rely.

The funeral relied for its power on the fact that both victims and perpetrators witnessed the reburial.

Thus, the other constituents (the required complement headed by on and any possible modifiers) of the verb phrase headed by rely are clearly separate from it.

Supposing one seeks a further reason not to consider rely on as a constituent, if it were considered a constituent there'd also be the need for a unit intermediate between verb and verb phrase that would have to be created in order to account for 'the verb and the word heading its required complement, but excluding any dependents in that complement' - an awfully specific and entirely unnecessary unit.

The analysis that works in all situations quite cleanly is clearly the one to be preferred: Rely is the head (constituent A) of the verb phrase. On and any dependents thereof form a complement (constituent B) in the verb phrase headed by rely. The complement headed by on is a required one (it may also be headed by upon, whereon, thereon etc.).


The choice of the constituents' structure depends on the semantics of the particular construction. According to Merriam-Webster's Dictionary: CONSTITUENT -  a structural unit of a definable syntactic, semantic, or phonological category that consists of one or more linguistic elements (such as words, morphemes, or features) and that can occur as a component of a larger construction. That's why first we must define this construction as either a prepositional verb (verb + preposition) or an idiomatic verb (verb + 'postfix'). For example: To look out (= to be careful) is an idiom. To look out (of the window) is a verb with a preposition. As about 'to rely on' it is a prepositional verb (not an idiom). Then the only possible costituents' analysis is 'to rely + on smb'.

  • 1
    Still, the OP suggests several bits of evidence supporting the opposite analysis too, so... wouldn't it be more prudent to simply say that there is no absolute truth here, but that we could actually argue for either analysis?
    – Hannah
    Jan 3, 2019 at 15:38

The "on" or "upon" prepositional phrase in "Mary relies (up)on John" tells where Mary places, or rests, her reliance. "Rely on" is no more a unit than "sit on", despite the meaning being less literal than "Mary lies (up)on John."

There is nothing wrong with saying "On John she relied, to help with record keeping."

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