Oxford dictionary of English says :
alone
2. [as adverb] Indicating that something is confined to the specified subject or recipient.
‘it was a smile for him alone’
It seems to me that "alone" functions as a part of a reduced relative clause. I'd say "alone" is an adjective.
In your opinion, what is the full, unreduced relative clause that corresponds to the reduced clause you're talking about? I don't see it. You might analyze 'alone' as a modifier of the prepositional phrase 'for him' because you can say 'only for him'.
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In your opinion, what is the full, unreduced relative clause that corresponds to the reduced clause you're talking about? I don't see it.
You might analyze 'alone' as a modifier of the prepositional phrase 'for him' because you can say 'only for him'. It's just that, by convention, 'only' is placed before the phrase, and 'alone' is placed after it. The meaning is the same either way.
It was a smile for him alone.
No, there's no relative clause here; why would you think that?
Here, "alone" is an adverb serving as a restrictive focusing modifier in NP structure, with "him" as its focus, not "for him" ("alone" follows the preposition so we know it's part of the NP, not the PP). "Alone" is unusual in that it usually occurs immediately af