What is comma before which?

When to use a comma before "which" depends on whether the clause introduced by "which" is restrictive (also called essential) or nonrestrictive (also called non-essential).

• Nonrestrictive Clauses: Use a comma before "which" when the clause it introduces provides extra, non-essential information. This information is interesting but not crucial to understanding the sentence's core meaning. The sentence would still make sense if the clause were removed. These clauses are sometimes called <a href="https://www.wikiwhat.page/kavramlar/nonrestrictive%20clause">nonrestrictive clause</a> or nonessential.

  • Example: "My car, which is very old, still runs well." The fact that the car is old is extra information.

• Restrictive Clauses: Do not use a comma before "which" when the clause it introduces is essential to understanding the sentence's meaning. This clause restricts or limits the noun it modifies. Removing the clause would change the meaning significantly. These clauses are sometimes called <a href="https://www.wikiwhat.page/kavramlar/restrictive%20clause">restrictive clause</a> or essential. "That" is often used instead of "which" in restrictive clauses in American English.

  • Example: "The car which is parked outside is mine." This identifies which car is being referred to.

In summary:

• Comma + "which": <a href="https://www.wikiwhat.page/kavramlar/nonrestrictive%20clause">Nonrestrictive clause</a> (extra information).
• No comma + "which": <a href="https://www.wikiwhat.page/kavramlar/restrictive%20clause">Restrictive clause</a> (essential information). Often "that" is preferred in restrictive clauses.