Zero Relative Pronoun

In English grammar, a zero relative pronoun is the missing element at the beginning of a relative clause in which the relative pronoun has been omitted. Also called a bare relative, zero relativizer, or empty operator.

In standard English, the zero relative pronoun can't serve as the subject of the main verb in the clause. Relative clauses headed by zeros (represented as Ø in the examples below) are sometimes called contact clauses or contact relatives.

Examples and Observations

• The house Ø I bought last year had sustained some fire damage.
• The woman Ø I hired to look after my mother is wonderful.
• I disagreed with most of the points Ø she raised.
• The book Ø he selected was Walden.
• Annie Dillard
  My parents let me set up my laboratory in the basement, where they wouldn't have to smell the urine Ø I collected in test tubes and kept in the vain hope it would grow something horrible.
• Stuart Prebble
  [G]rumps generally don't have the slightest idea what people will want, so they end up buying something Ø they would like to receive themselves. And that simply doubles the problem: the person who receives it doesn't want it, and the person Ø you gave it to now has something you want yourself, which just makes you want it more.

​When to Use the Zero Relative Pronoun

• M. Strumpf and A. Douglas​
  On occasion, we can correctly omit the relative pronoun from a relative clause. The gap left by the omitted pronoun is called a zero relative pronoun. If the omission does not bring a verb to the head of the relative clause, it is perfectly correct to remove the relative pronoun. The sentence will make complete sense without it.
  The car ( that) we saw yesterday was too expensive.
  The people ( whom) we know are not very responsible.
  In each example, the omitted relative pronoun is in parenthesis because it is optional. In the first example, the relative clause we saw yesterday modifies the noun car. We could write the clause with the relative pronoun that included, but we do not have to. In the second example, the relative clause we know modifies the noun people. We could have included the relative pronoun whom in the clause, but the sentence makes perfect sense without it.
  In other sentences, removing the relative pronoun would make a verb the first word in the clause and cause the sentence to be grammatically incomplete.
  The men who repaired our roof did a wonderful job. (correct)
  We all saw the show that won the Tony Award this year. (correct) Try leaving off the relative pronoun in each example.
  The men repaired our roof did a wonderful job. (incorrect)
  We all saw the show won the Tony Award this year. (incorrect)
  These sentences do not amount to much. When appropriate, feel free to use a relative clause containing a zero relative pronoun. Just be sure that your sentence still makes sense.

The Zero Relative Pronoun and Syntactic Ambiguity

• Tony McEnery and Andrew Hardie​
  [I]f a zero relative pronoun is used, it may be possible for the first word of the relative clause to be interpreted as part of the main clause; Temperley [2003] gives the example phrase the biological toll logging can take, where the first four words are ambiguous on an initial reading--logging may be the head noun of the NP or the subject of the upcoming relative clause--the ambiguity only being resolved on the word can, which as a modal verb indicates that the word before it is more likely to have been a subject.