a relative clause that describes or supplements but is not essential in establishing the identity of the antecedent and is usually set off by commas in English. In This year, which has been dry, is bad for crops the clause which has been dry is a nonrestrictive clause.
Compare restrictive clause.
Origin of nonrestrictive clause
First recorded in 1925–30
Also called descriptive clause.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019