I have recently been learning about complementisers and relative clauses etc. and how they relate to x-bar theory. It is a feature of English that some complementisers are optional, especially in spoken English, e.g. "I think (that) you are great".

This is also true for relative clauses: "The person (that) I saw yesterday"; "The ball (that is) on the table".

However, sometimes they are not optional: "The dog that is red" --> *"The dog red".

I suppose what I mean is, is there a way of telling when "that is" is a not-present optional complementiser, and when it is actually not present?

For example, with one of the above sentences, is "that is" really implied in the NP, "The ball on the table", or is it simply not there at all?

More particularly, with adjectives like 'available':

"The bread available in the bakery looks delicious".

Does this sentence contain an implied "that is", i.e. it is really a contracted way of saying "The bread THAT IS available in the bakery looks delicious", or does it actually not contain or imply at all "that is"?

This relates to x-bar theory, or rather phrase structure rules, in that normally adjective phrases are not allowed to come after a noun (except in poetic usage etc.), so if "available in the bakery" is an adjective phrase (not a relative clause), why can it come after the noun "bread"?

[in this question I have assumed that "that is" is a complementiser just like "that"; I admit I am not totally sure about this]


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    @jlawler Whiz deletion is just giving a term to the phenomenon being asked about. The question is, essentially, how do you tell whether a noun + post-modifier phrase is an instance of whiz deletion or not? Do you consider all post-modifiers to be whiz-deletions (in which case you’d be contradicting @Keelan)? How do you tell the difference between a whiz-deleted (and therefore on the surface nonexistent) relativiser + copula and a phrase that actually has no relativiser + copula at all? Oct 7, 2021 at 23:24
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    @jlawler Well, it's not a biconditional relationship, because in the other direction many relative clauses cannot be reduced (essentially, those ones which would result in phrases which cannot postmodify nouns). So we cannot reduce "panda that was ill" or"panda who was a mathematician", for example. Sep 2, 2022 at 8:49
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    Because those are one-word modifiers, not modifiers of more than one word. The null hypothesis is that relative clauses are the full expansions of modifiers, and they get reduced as needed by several processes until they decay to one-word status and precede. Like matter around a black hole.
    – jlawler
    Sep 2, 2022 at 14:37
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    @jlawler But how about "the panda who was the first animal mathematician to win the Fields medal"? Why does that not work? Sep 2, 2022 at 23:47
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    The man who was the first linguist on the Moon is grammatical, if verbose. And whiz deletion doesn't work, granted. But why should it? The NP has been extended by clefting on an unnecessary man who was instead of just saying the first linguist on the Moon, so shortening it is silly. Pick one, longer or shorter, but not both. Similarly for panda mathematicians; if you want to cram that much info into one noun phrase, don't go around busting seams.
    – jlawler
    Sep 3, 2022 at 1:49


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