My mother is now back with us.

Does "back" in the sentence function as an adverb? Can adverb phrase function as subject complement?

  • 1
    Could you tell us what you mean by "subject complement"? – F.E. Dec 18 '14 at 7:48
  • I think "subject complement" provides more information about the subject. – April Dec 18 '14 at 12:57
  • From the logical side, one would simply call it a predicate or predicate phrase, which can syntactically be an adverb or adverb phrase, an adjective or adjective phrase, or a noun or noun phrase -- when appearing with the appropriate auxiliary. – John Lawler May 14 '17 at 3:07

My mother is now back with us.

The phrase back with us is a preposition phrase. It is headed by the preposition back. The Original Poster asks if back can be considered a subject complement. It does indeed describe the subject, my mother. Because it tells us the location of my mother, we call it a locative complement.

We often use preposition phrases as locative complements:

  • My elephant is in Spain.
  • There is a man outside.
  • The beer is on the table.

We can show that back is a preposition and not an adverb. The Original Poster asks whether adverbs can function as Subject Complement. The answer is that adverbs can NOT normally function as complements of the verb BE - but prepositions and preposition phrases can:

Adverbs as complements of BE

  • *She was happily (ungrammatical)
  • *The elephant was locally. (ungrammatical)
  • *The assassin was viciously. (ungrammatical)

Preposition Phrases as complements of BE

  • She was in the shop.
  • She was out.
  • She was back.
  • She was back at home.

Also, adverbs can't usually modify noun phrases. Prepositions and preposition phrases can:

Adverbs modifying nouns

  • *the beautifully woman (ungrammatical)
  • *the woman beautifully (ungrammatical)

Preposition Phrases modifying nouns

  • her indoors
  • my friends back at home
  • the man in the shop
  • the man of the moment

In addition, adverbs can usually be modified by the adverb very, prepositions usually cannot:

Adverbs modified by very

  • He danced very beutifully.
  • She'll be here very soon.
  • My baboon ate very loudly.

Prepositions modified by very

  • She was very in trouble. (ungrammatical)
  • He was very back. (ungrammatical)
  • My elephant was very behind the door. (ungrammatical)

Lastly, most prepositions and preposition phrases can be modified by the special adverbs straight and right. Adverbs cannot usually be modified by straight or right:

Adverbs modified by straight or right

  • *She lived right locally. (ungrammatical)
  • *I'll be there right soon. (ungrammatical)
  • *She shouted straight dramatically. (ungrammatical)

Prepositions modified by straight or right

  • She went straight into the building.
  • My elephant jumped right over the table.
  • Go straight on.
  • Come straight back.
  • She's right back where she belongs

The Original Poster's question

In the Original Poster's example the preposition back has another preposition phrase as its complement. The complement of the preposition back is with us. This second preposition phrase has the preposition with as its head. The complement of with is the pronoun us. The whole preposition phrase back with us functions as the complement of the verb BE. It is a locative complement telling us the location of the subject, My mother.

Adverbs, on the other hand, do not usually function as complements of the verb BE. We do not usually find them, therefore, as subject complements.

Hope this is helpful!

  • 1
    Hey, that's a nice post! :) -- The reason I asked the OP that question was to see if their grammar was using the term "subject complement" to mean "subjective predicative complement" (PC), and so, if it did, then that might significantly affect the answer. – F.E. Dec 18 '14 at 16:25
  • And so, is "back" a so-called subject complement in the OP's example? I'm asking because I'm seeing "Tom is in the house" and "Tom is playing in the house" as being similar w.r.t. "in the house" and wonder if that locative would be considered to be a subject complement in both? :) -- I've found a bit in 1985 Quirk et al., pg 55, "2.18 Obligatory adverbials", which treats the locative different from PC (also, pg 733. Also, another poster found an excerpt in a dictionary that supports the locative as subject complement. Are there common grammar sources that teach locative as PC? – F.E. Dec 19 '14 at 18:41
  • What resource(s) did you consult for all that? Or did you spit it all out from memory? In the meantime, some dialects of AmE do allow She'll be here right soon. – user6951 Dec 20 '14 at 8:18
  • 1
    Er, don't you make me hafta write an answer post on this! There's NFL games on today and tomorrow, besides all the other stuff I'm supposed to be doing! :D – F.E. Dec 20 '14 at 19:36
  • 1
    @F.E. Maybe you should though. In particular, H&P 2005 talk about 'subjective' and 'objective' complements. Now they use PCs to illustrate, but they don't in any way limit subjective and objective complements to being PCs as far as I can see, On the other hand they don't even mention them in the first place in 2002. Btw, sorry but don't have 2005 to hand, so you'd need to look them up in the index... I'm of course making the leap that 'subjective' complements are what other people call subject complements, but who knows? It's clear that a locative complement could apply to either S or DO ... – Araucaria - Not here any more. Dec 22 '14 at 3:13

In your sentence, 'back' is being used as an adverb of place. I think the issue here is that 'Mother' (a person) cannot equal 'back' (a location). You can't have a 'back mother.' That is nonsense.

But an adverbial phrase CAN be a subject complement. I'll throw this out:

You have to be smarter than the horse you are riding.

In this example, 'smarter' is a complement to the subject, 'you.' The two are equivalent. In this case, 'You' (a person) can equal 'smarter' (an adjective). A big man. A yellow horse. These are possible. A 'smarter you' is also completely possible.

'Smarter than the horse' also happens to be an adverbial phrase of comparison. 'Than' is a correlative conjunction, connecting the grammatically equal 'you' and 'horse.' So the phrase 'smarter than the horse' becomes -- as a whole -- a subject complement. And it is an adverbial phrase. Behold, the two are one.

But I can't leave something unfinished. So:

'You are riding' has an elided 'that,' making it a non-defining relative clause.

I believe 'to be' is an infinitive direct object to 'have,' though some might consider 'have to be' a complex verb. For me, it is easier to think of infinitives as a discrete units functioning in specific ways instead of tacking them to whatever happens to be close by.

  • "You have to be smarter" - the verb 'have' is a state verb meaning the subject expereinces a state where some action or state is required from them. The subject has, must, is required + to do some action. 'to be' is an infifnitve verb phrase that is part of a compound verb complement phrase (to be + smarter) the compound relatin is an object of the main verb but 'smarter' is the complement of the non-finite verb 'be'. so in this nonfinte clause smarter is a comparative adjective as an adverbial saying how the subject should exist. The meaning of the verb is slected by the complement form. – Ubu English Dec 13 '20 at 6:40

Yes, an adverb can also function as a subject complement in some cases. The word "back" in the sentence "My mother is now back with us" has been used as an adverb.

Cambridge English Grammar Today states:

"Subject complements can be adjective phrases, noun phrases, adverb phrases or prepositional phrases. I am upstairs (subject + adverb)".

  • Could you please provide a grammar source for that? – F.E. Dec 18 '14 at 7:45
  • 1
  • You might want to consider putting an excerpt from that dictionary into your answer post, since that will help support your answer, and it will also let others know where you are coming from. – F.E. Dec 19 '14 at 18:13
  • @F.E/A nice piece of advice! I have edited my answer accordingly. – Khan Dec 20 '14 at 5:13

My mother is now back with us

This is not a link verb + subject complement construction.

(Note: I use the term complement loosely - as any word phrase that adds information to another word phrase. They do not need to be required to be called a complement.)

Sometimes BE functions as a state verb, meaning 'to exist'. This is almost always the case when BE takes a prepositional phrase as a verb complement. Noun phrases and adjective phrases after BE almost always select BE as a linking verb. Further, prepositional phrases as main verb complements almost always function adverbially (to say where, when, why, how the action or state occur).

Also, back with us is a not an adverb or an adverb phrase, it's a compound adverbial (adverb phrase + prepositional phrase). with us is an adverb complement - it is adding information to the adverb back. The compound adverbial locates where the state of 'existence' or 'being' takes place (back with us) but that doesn't make it an adverb.

It's actually the relation between the subject and the main verb that locates the state in the subject. The subjects of state verbs generally take the semantic role of possessor of that state.

So, in terms of the OP question, the only adverbs in your sentence are now and back. now is superfluous (the verb is already present tense), and it has no direct relation to the subject - it is both syntactically and semantically a verb complement.

Back is an adverb phrase as a verb complement meaning roughly (to return). With us is an adverb complement adding information to back. Together they form a compound adverbial.

My mother is back with us. S|V|A[AVP + avc(pp):back] + a(avp)


  • A = verb complement in a core adverbial relation
  • a = verb coplement in non-core adverbial relation
  • AVP = adverb phrase (core)
  • avp = adverb phrase (not core)
  • avc = adverb complement
  • [...] = a compound adverbial phrase

Does "back" in the sentence function as an adverb?

Yes, it is an adverb. But it is not a subject complement. It is saying where the verb occurs (back with us).

Can adverb phrase function as subject complement?

No, I don't think so. Maybe never, but possibly with non-finite clauses.


Adverb indicates a word function (class/PoS).

Adverb phrase indicates a word phrase type (one with an adverb at its head)

Adverbial indicates a word phrase or group of syntactically linked word phrases that function as verb complements to the main verb to say where, when, why or how the verb occurs.

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