noun Date: 1916 a descriptive clause that is not essential to the definiteness of the meaning of the word it modifies (as who is retired in “my father, who is retired, does volunteer work”)
NONRESTRICTIVE CLAUSE
Meaning of NONRESTRICTIVE CLAUSE in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012