supplementary relative clause

English

Examples
His sister Mary, who has been married five times, was left a considerable fortune. The washing machine has broken down, which isn't good news.

Noun

supplementary relative clause (plural supplementary relative clauses)

1. (grammar) A relative clause, usually set off by a comma or commas, that provides additional information about the person or thing referred to, or about a statement that has been made, as opposed to information that is essential to specifying or identifying who or what is meant.

   Synonyms: non-restrictive relative clause, non-defining relative clause

   Antonyms: integrated relative clause, restrictive relative clause, defining relative clause

   Hypernyms: supplement; relative clause < subordinate clause < clause

   • 2024, Geoffrey K. Pullum, The Truth About English Grammar, Polity Press, →ISBN, page 112:

     Supplementary relative clauses (which other books call “appositive relatives” or “non-restrictive relatives”) are optional parenthetical interruptions of sentences. They can always be left out without changing the main assertion (though the ancillary information they contribute will be gone). The most important thing to remember about them in writing is that they must be separated off by punctuation, typically commas: The duke, [who the organizers had hoped __ would present the award], was unable to attend owing to illness.