Section 13.10 Relative Clauses: Overview
Of all adjectival structures, relative clauses are the most complex because they are full clauses—with their own subject and predicate—embedded inside a noun phrase. The connecting element is a relative pronoun (who, which, that) or relative adverb (where, when) that simultaneously introduces the clause and fills a grammatical role within it.
How Relative Clauses Compare to Other Adjectivals.
Each adjectival form adds a different degree of structural complexity to the noun phrase. Adjective phrases and noun adjectivals are single words or tight word groups that slot directly before the head noun. Prepositional phrases add one layer of embedding—a preposition linking the noun to a following noun phrase. Participial phrases go one step further: they retain the verb’s form and can take their own complements, but they lack a subject of their own. Relative clauses are the only adjectival that contains a full subject-predicate structure. This makes them the most flexible and informative of the adjectival types, but also the heaviest—and the one most likely to create attachment and parsing difficulties in long sentences.
Where Relative Clauses Appear.
Relative clauses are always post-nominal: they follow the noun they modify and cannot precede it. You can say the student who won the prize, but not the who won the prize student. This positional constraint holds regardless of whether the clause is restrictive or non-restrictive. See Section 13.4 for the restrictive/non-restrictive distinction, which is especially important for relative clauses: a restrictive relative clause (no commas) identifies which referent is meant, while a non-restrictive relative clause (set off with commas) adds supplementary information about an already-identified referent.
Two Structural Patterns.
Relative clauses come in two broad structural patterns depending on the grammatical role of the relative pronoun inside the clause. In the first pattern, the relative pronoun is the subject of the embedded clause:
[RC [NP [REL who]] [VP ...]]. In the second, the relative pronoun is the object, and a separate subject NP follows it: [RC [REL whom] [NP ...] [VP ...]]. These two patterns have different implications for word order, pronoun choice (who vs. whom), and whether the relative pronoun can be omitted. The next section examines these patterns in detail with diagrams.
