I'm looking for the translation of the mathematical term Partie stable.
I appreciate any suggestions.
Partie means "subset."
The term partie stable would be translated as "stable subset."
Or: "A subset stable under a function f [or closed under an operation X]."
Let f be a mapping from a set E to itself, and let S be a subset of E. The subset S is said to be stable under f if f(S) is contained in S.