non-restrictive usage
Linguistics term for a relative clause that adds extra information without limiting the noun's reference. Contrasts with 制限用法 (restrictive usage).
See also: 制限用法
English relative pronouns have restrictive and non-restrictive usage.
In non-restrictive usage, it is often set off by commas.
制限用法 is restrictive usage, which limits the noun's reference; 非制限用法 adds non-essential information.
Compound of 非 (non-) + 制限 (restriction) + 用法 (usage), a calque from English 'non-restrictive usage'.