# isStrictSubset(of:) Returns a Boolean value that indicates whether the set is a strict subset of the given sequence. ``` func isStrictSubset(of possibleStrictSuperset: S) -> Bool where Element == S.Element, S : Sequence ``` ## Parameters `possibleStrictSuperset` A sequence of elements. `possibleStrictSuperset` must be finite. ## Return Value `true` is the set is strict subset of `possibleStrictSuperset`; otherwise, `false`. ## Discussion Set *A* is a strict subset of another set *B* if every member of *A* is also a member of *B* and *B* contains at least one element that is not a member of *A*. ``` let employees = ["Alicia", "Bethany", "Chris", "Diana", "Eric"] let attendees: Set = ["Alicia", "Bethany", "Diana"] print(attendees.isStrictSubset(of: employees)) // Prints "true" // A set is never a strict subset of itself: print(attendees.isStrictSubset(of: attendees)) // Prints "false" ``` --- 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)