Numerosity, Commonality, Typicality, and Adequacy
The four threshold requirements every proposed class must satisfy under Rule 23(a) before a court will even consider which type of class it might be.
Numerosity asks whether the class is large enough that joining every member as an individual plaintiff would be impractical; courts commonly treat classes over roughly 40 members as satisfying this element, though there is no fixed number in the rule itself. Commonality asks whether the class shares at least one question of law or fact whose resolution will drive the litigation forward for everyone.
Typicality asks whether the named plaintiff's claims arise from the same course of conduct and legal theory as the class, so that in pursuing their own case the representative necessarily advances everyone else's. Adequacy asks whether the representative and class counsel have interests aligned with the class and no disqualifying conflicts, and whether counsel has the resources and experience to litigate the case competently.
Because these four elements are conjunctive, Juricratic's certification models track each one as a separate sub-dial rather than a single composite probability — a matter can be strong on commonality and evidence quality but structurally weak on typicality if the named plaintiff's facts diverge from the class in a way that shows up early in discovery.
How it actually shows up
Litigators build a fact record — deposition testimony, expert reports, and a class definition — aimed at each of the four elements independently, since a certification motion typically wins or loses on whichever single element is weakest, not on the overall strength of the case.
- How many class members are needed to satisfy numerosity?
- There is no fixed number in Rule 23, but courts frequently treat classes of roughly 40 or more members as satisfying numerosity, while smaller classes require a more specific showing that joinder is impractical.
- What is the difference between commonality and typicality?
- Commonality looks at whether the class shares common questions; typicality looks at whether the named plaintiff's individual claim is representative enough of those common questions to fairly stand in for the class.
- Why does adequacy sometimes defeat certification even when the claims are strong?
- A representative with unique defenses, a conflict of interest with other class members, or inexperienced counsel can fail adequacy even if the substantive legal theory is sound, because adequacy protects absent members who are bound without personally litigating.
This page is an educational explainer, not legal advice, and creates no attorney–client relationship. Juricratic is a simulation engine: every probability-like figure is a dial you set, not a calibrated prediction. Verify every rule, deadline, and figure against the authorities and orders that govern your matter.
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