nonrestrictive

adjective

1. not restrictive
2. Gram. designating a modifier, as a word, phrase, or subordinate clause, that does not limit the reference of the word or phrase it modifies but merely adds information and thus is not essential to the meaning of a sentence: it is set off by punctuation marks: “who is six feet tall” in “John, who is six feet tall, is younger than Bill” is a nonrestrictive clause