User:Dan Polansky/Which vs that

Some grammarians want to restrain "which" to non-restrictive clauses, as opposed to restrictive clauses; for restrictive clauses, they prescribe "that". It seems that native English speakers very often violate this rule. As a consequence, the rule seems to fail to describe prevalent patterns of actual usage.

Promulgators of the rule: Fowlers as a wish rule, White (but not Strunk) as an actual rule, as per G. K. Pullum.

For terminology, see Google Ngram Viewer for restrictive clauses, nonrestrictive clauses, defining clauses, essential clauses, nonessential clauses.