# formIntersection(_:) Removes the elements of the set that aren’t also in the given sequence. ``` mutating func formIntersection(_ other: S) where Element == S.Element, S : Sequence ``` ## Parameters `other` A sequence of elements. `other` must be finite. ## Discussion In the following example, the elements of the `employees` set that are not also members of the `neighbors` set are removed. In particular, the names `"Alicia"`, `"Chris"`, and `"Diana"` are removed. ``` var employees: Set = ["Alicia", "Bethany", "Chris", "Diana", "Eric"] let neighbors = ["Bethany", "Eric", "Forlani", "Greta"] employees.formIntersection(neighbors) print(employees) // Prints "["Bethany", "Eric"]" ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)