Can appositives be composed of adjectives?

Question

I’ve been reading a bit about apposition, and all the examples seem to be revolving around noun phrases. I’m wondering if adjectives can also form appositives.

Consider, for instance, the following two sentences:

This scenario could easily lead to a system that is too conservative, overdesigned.

The predictions delivered by these techniques are coarse, aggregate.

Assuming that too conservative means overdesigned, and that coarse means aggregate, are these two constructions legitimate appositives?

In addition, I’m interested in other ways of phrasing and punctuating the above sentences. Specifically, is it grammatical to write as follows?

1. This scenario could easily lead to a system that is too conservative, or overdesigned.

2. This scenario could easily lead to a system that is too conservative—or overdesigned.

I suppose that, if I leave out the comma and the em dash as shown below, the meaning of the sentence will change, which also needs a confirmation.

3. This scenario could easily lead to a system that is too conservative or overdesigned.

If “A, B”, “A, or B”, and “A—B” at the end of sentences are grammatical, why is it legitimate to write like this? What is the explanation? How are these three constructions called?

Answer 1

Some dictionaries, such as Merriam-Webster, define "apposition" solely in terms of nouns or "noun equivalents". Other sources give a vaguer definition: Oxford Living Dictionaries refers to "a relationship between two or more words or phrases in which the two units are grammatically parallel and have the same referent". The full OED defines "apposition" broadly before giving a narrower, more specific definition:

Grammar. The placing of a word beside, or in syntactic parallelism with, another; spec. the addition of one substantive to another, or to a noun clause, as an attribute or complement; the position of the substantive so added.

In Quirk, Greenbaum, Leech and Svartvik, A Comprehensive Grammar of the English Language (Longman, 1985), it is contended that relations between adjectives can be "appositive-like" but that the term "apposition" should be reserved for noun phrases. In section 17.74, the authors write:

Appositive-like relations exist also between other units than noun phrase, such as clauses [4], predications [5], and adjectives [6].

Although she was reluctant, although she felt an understandable hesitation, she eventually agreed. [4]

They had summoned help - called the police and fire brigade. [5]

She is better, very much better, than she used to be. [6]

However, to talk about apposition of units other than noun phrases makes the concept of apposition too weak. Such apposition-like constructions will be treated as exceptional.

Huddleston & Pullum, The Cambridge Grammar of the English Language, also reserves the term "apposition" for noun phrases.

On the other hand, Otto Jespersen (Essentials of English Grammar) uses a much broader definition to "apposition". Jespersen states, for example, that "participles are very often placed in apposition, either after or before the word they qualify". His examples include:

He came back, utterly exhausted, from his long ride.

She went out, having first locked the drawer carefully.

But Essentials was published in 1933. I feel pretty sure that Huddleston & Pullum and Quirk et al. are more representative of today's consensus.

Answer 2

OP writes:

I’m interested in other ways of phrasing and punctuating the ... sentences.

This scenario could easily lead to a system that is too conservative, overdesigned.

The predictions delivered by these techniques are coarse, aggregate.

I don't see conservative as being synonymous with overdesigned, and would therefore link these adjectives with AND or OR:

This scenario could easily lead to a system that is overdesigned and too conservative.

This scenario could easily lead to a system that is either overdesigned or too conservative.

I deal frequently with aggregated data but I wouldn't know what an aggregate prediction was exactly:

The predictions delivered by these techniques are coarse, aggregate.

Also, asyndeton is better suited to prose that seeks to evoke than it is to prose that seeks to explain.

Perhaps you might want to say what these techniques cannot do:

These techniques cannot deliver precise predictions.