AI Tutor
Imagine texting a friend: "My brother who lives in Dallas is a pilot." Without realizing it, you just told them you have at least two brothers.
A relative clause is a dependent clause that starts with a relative pronounβ€”such as who, which, or thatβ€”and gives more information about a preceding noun called the antecedent.
Why does punctuation change the number of brothers you have? The answer comes down to whether that clause is restrictive or nonrestrictive.

Restrictive Clauses: The Essential Identifiers

A restrictive clause delivers essential information required to pinpoint exactly which noun you are talking about. Because the information is necessary to identify the noun, you use no commas around it.
What happens when the noun is already unique and needs no narrowing down at all?

Nonrestrictive Clauses: Bonus Commentary

A nonrestrictive clause adds extra, nonessential description to a noun that is already fully identified. Because you can delete the clause without changing the core identity of the noun, you must set it off with commas.
How do you know whether to write that or which when referring to objects and concepts?

Choosing the Right Relative Pronoun