Let E$E$ be a set, and let S$S$ be any set of subsets of E$E$, such that S$S$ contains the emptysetempty set. Can you identify the smallest set of subsets T$T$ of E$E$ such that T$T$ contains all elements of S$S$, and T$T$ is stable by both finite union and by any intersections ? If possible write the generic form of an élémentelement of T$T$ by using élémentselements of S$S$, with unions and intersections.