It's more headache than it's worth.
It's more trouble than it's worth.
Is this "worth" adjective or noun?
I think the adjective "worth" needs an object after it.
However, there is no object of worth in this sentence.
What is the wordclass of this "worth"?
Seeing this typical question about parts of speech, with its typically confident assertions in reply that X is this part of speech, or that part of speech, reminds me that such questions have no good answers in English, and even if answered confidently, such assertions carry no information beyond the certainty of the asserter.
In English, pretty much any word can be used for any part of speech, and we have not yet been vouchsafed a vision of the true, the blushful, the Real Parts of Speech for English. Though it is fun to argue about them, like dragons and unicorns and DPs and other mythical beasts. Worth is a really good example of where the POS system falls down.
I published a paper many years ago about the meanings and uses of the English words value, worth, price, and cost, which all stem from the same set of contexts. What it says on p.391 about the grammatical category of worth is:
"the categorial status of worth is a matter of some dispute. It has variously been claimed to be a preposition and an adjective (cf Maling 1983 and McCawley 1985). If it is a preposition, then it must have a homophonous derived noun, since phrases like the worth of the book are common enough. On the other hand, if it is an adjective, then it must be transitive, since it has a complement; this is surely unusual -- or even impossible, according to some theories of grammatical categories. I will have nothing to say about the categorial status of worth here, since the matter is irrelevant to its meaning; let it stand that no matter what category worth may belong to, it is an atypical example of the category."
- Heny, Frank; and Richards, Barry (eds). 1983. Linguistic Categories: Auxiliaries and related puzzles (2 Vols). Dordrech: Reidel.
- Maling, Joan. 1983. "Transitive adjectives: A case of categorial reanalysis." In Heny and Richards 1983.
- McCawley, James D. 1985. Review article on Heny and Richards (eds) 1983. In Language, vol 61, pp 849-62.
The idiomatic phrases are
It's worth the trouble.
and
It's worth the headache.
where what you call objects are in italics.
More trouble than it's worth (and I would add here more headache than it's worth as a synonym] is an idiom which Cambridge defines as
idiom informal (also not worth the trouble)
If something is more trouble than it's worth or is not worth the trouble, it is not important or useful enough to make an effort doing it.
Worth is one of the few transitive adjectives in English. You can find an extended argument that worth belongs to the category of adjectives in CAGEL pp. 607-608.
These transitive adjectives take what Rodney Huddleston calls noun phrase (NP) complements. LanguageLog explains:
English adjectives generally don't take NP complements. The number of exceptions is extraordinarily small: one example is worth (notice how we say worth my time, not *worth of my time). Such exceptional adjectives have long been noted; Fowler comments on worth in his Modern English Usage (1926), and points out that it could be called a transitive adjective. But such adjectives are extremely rare in the dictionary. And yet some new ones appear to have been creeping into the language.
In your two examples, the 2 NP complements are omitted to avoid repetition.
Note: The rest of the adjectives which are intransitive can take complements, but not Noun Phrases complements.
Dictionaries mention "worth" as an adjective. (Cambridge, Collins, Longman, Mcmillan, American Heritage)
However, not all are as categorical.
(OALD) worth adjective [not before noun] used like a preposition, followed by a noun, pronoun or number, or by the -ing form of a verb
The SOED, while still considering this word to be an adjective, makes an important distinction.
(SOED) pred. a. (now usu. w. prepositional force)
Merriam-Webster goes all the way and defines "worth" as a preposition.
From a syntactic point of view this is a word that qualifies only with difficulty to only one of the criteria for adjectives; out of the four features it can be said that only the possibility of finding it in predicative use can be considered. It does not qualify nouns in attributive use (a worth thing), premodification by "very" is not possible (very worth) and finally it does not stand the test of comparisons (more worth than, "worthy" does). As to predicative use, there is much that can be said that shows that this also is dubious; the following are not possible, yet correspond to true predicative use.
In my opinion such constructions stem from the oversimplification of longer constructions in which "worth" is the noun, and they have now an idiomatic status in the language.
