Postmodifiers include prepositional phrases, relative clauses, to-clauses, ed-clauses, ing-clauses, and a few others.
Nouns are often post-modified with prepositional phrases. In fact this is the commonest form of noun postmodification.
A prepositional phrase consists of a preposition and a complement. The complement is usually a noun phrase, but it could be other types as we will see later.
All these examples consist of headword, a preposition, and a noun phrase. In this case all of the noun phrases except the last consist of a single noun. In the last case the noun phrase consists of the noun "patterns" modified by another noun "sleep". Prepositional phrases can be much longer and more complex than this.
Nouns are often post-modified with a relative clause. Sometimes a prepositional phrase can easily be expressed as a relative clause. For example we could change "rocks like basalt" into "rocks which are like basalt".
A relative clause consists of a relativizer which connects the clause to the head noun plus the clause itself. The relativizer points back (anaphorically) to the the head noun. This is sometimes called the antecedent.
Relativizers are relative pronouns (who, which, whose, that, whom) or relative adverbs (when, where, why).
Relative clauses are also divided into two main types (restrictive and non-restrictive). In restrictive clauses the postmodifier is closely identified with the head noun; it has a defining function. In non-restrictive clauses the postmodifier serves to add more information about the head word. Non-restrictive clauses are separated from the head noun by a comma.
All these examples consist of headword, and a finite relative clause containing a relativizer. The first example is a non-restrictive relative clause which gives some extra information about the head noun. All the others are restrictive relative clauses which define or restrict the meaning of the head noun.
Nouns are sometimes post-modified with a to-clause. These are non-finite clauses, usually without a subject.
The to-clause gives more information about the headword. Often, the main clause containing the headword would have little meaning without the to-clause.
You can see from examples 2 and 4 above that the modification may apply not just to a single noun but also to a noun phrase. In example 2 we have "protein isolates and other chemicals" and in example 4 "methods and guidelines". These are binomial phrases and they are seen mostly in academic writing, but there are a few in common use, for example "husband and wife", "food and drink".
You can also see from example 4 that there are in fact two to-clauses, 1) "to recover and interpret authentic DNA" and 2) "to minimise the risk of contamination from modern sources ... ". In fact, you could say there are three: "to recover ..", "(to) interpret ..", and "to minimise ..".
Nouns are sometimes post-modified with ed-clauses. These are non-finite participle clauses.
The ed-clause gives more information about the headword. Ed-clauses can easily be rewritten as passives (e.g. "research published in Nature" = "research which was published in Nature").
These phrases are called ed-phrases because they use the past-participle of verbs. But the past-participle of irregular verbs don't end in "ed", as you can see from examples 2 and 3 above.
In all of these examples the ed-clause could be rewritten as a relative clause with a verb in the passive voice. Ed-clauses have the advantage of being shorter.
Nouns are sometimes post-modified with ing-clauses. These are also non-finite participle clauses.
The ing-clause gives more information about the headword. Ing-clauses are less common than ed-clauses and cannot always be rewritten as a relative clause with a verb in the passive voice.
A few ing-participles occur much more frequently than other, including two in the examples above; containing and concerning. Others are being, involving, using, having, consisting, relating, resulting.
Nouns are sometimes post-modified with other noun phrases. In academic writing these noun phrases are used provide to extra information, clarification, examples, formulae, and acronyms. They may be enclosed by commas but are often enclosed in parentheses, as in the following examples.
In the above examples the first is an explanation (of what plasma is), the second is a list of examples of animals in the category of arthropods, the third is an acronym, and the last is a one word noun phrase giving the technical name for "chemical transmitters".