Commonality
Commonality means the class members' claims share a common question that a court can answer for all of them at once.
Also called: commonality requirement, Rule 23(a)(2), common questions of law or fact
Commonality means the class members' claims share a common question that a court can answer for all of them at once.
What it means
Commonality is the Rule 23(a)(2) requirement that there be "questions of law or fact common to the class." Put simply, the class members' claims need something real in common, not just a shared complaint.
The Supreme Court has said that the claims must depend on a common contention that a court can resolve for the whole class at once. Answering it must settle an issue that is central to every claim. "Did the company disclose this fee on the same checkout screen to every customer?" can be answered for everyone together. "Was each employee treated unfairly by a different manager?" usually cannot.
Commonality is one of the four Rule 23(a) tests, along with numerosity, typicality and adequacy. It overlaps with the predominance test for damages classes, which asks whether the common questions outweigh the individual ones.
What it means for you
Commonality is why class actions fit problems like a hidden fee, a data breach or a mislabeled product, where one company practice hit everyone the same way. It fits poorly when harms differ from person to person. For you, it is one reason class settlements often pay a flat amount or fixed tiers instead of an amount based on your personal story. If your situation really is different, such as a serious injury or a large documented loss, a class payment may not reflect it. Read the notice to see how losses are handled before you decide what to do.
Example
Say a meal-kit company adds a "processing fee" to every order but never shows it before checkout. Every customer's claim turns on one question: was the fee properly disclosed? One ruling answers it for all. Now say customers complain that boxes arrived late. Each delay had a different cause, so there is no single answer, and commonality is much harder to show.
FAQ
It is the Rule 23(a)(2) requirement that class members' claims share a common question that a court can answer for the whole class at once. Having the same type of claim is not enough if the facts differ from person to person.
No, though courts often treat them as closely linked. Commonality asks whether the class's claims share a central question. Typicality asks whether the named plaintiff's own claim is like the rest of the class's claims.
Related terms
- Fed. R. Civ. P. 23, Class Actions (Cornell Legal Information Institute)
- Wal-Mart Stores, Inc. v. Dukes, 564 U.S. 338 (2011) (U.S. Reports, Library of Congress)
Updated Oct 18, 2026. Plain-English definitions for general information — not legal or tax advice.