A more thorough explanation:

A pattern-or-practice case is a type of lawsuit where the plaintiff tries to prove that the defendant has engaged in discriminatory activities systematically. This is often done through policies and procedures that discriminate against a particular group of people. These cases usually involve employment discrimination, housing discrimination, or school segregation.

To win a pattern-or-practice case, the plaintiff must show that the defendant's behavior forms a pattern of actions or is embedded in routine practices. They must also show that the defendant has consistently failed to respond to complaints or implement corrective measures, which suggests executive or official complicity.

• An African American employee sues their employer for racial discrimination, claiming that the company has a policy of only promoting white employees to management positions.
• A group of tenants sues their landlord for housing discrimination, alleging that the landlord only rents to people of a certain race or ethnicity.
• A group of parents sues a school district for school segregation, arguing that the district's policies and practices have resulted in the segregation of students based on race.

These examples illustrate how a pattern-or-practice case can be used to challenge discriminatory policies and practices that affect a large group of people. By showing that the defendant's behavior is part of a pattern or routine practice, the plaintiff can demonstrate that the discrimination is not just an isolated incident but a systemic problem that needs to be addressed.