Technically, the correct HTML symbol for 'superset' (or, more fully, 'improper superset') is ⊇ (⊇). (A ⊇ B), or "A is an improper superset of B", means (∀ x : (x ∈ B) ⇒ (x ∈ A)). The ⊃ (⊃) symbol is for 'proper superset'. A ⊃ B, or "A is a proper superset of B", means ((A ⊇ B) ∧ (A ≠ B)), or equivalently, ((∀ x : (x ∈ B) ⇒ (x ∈ A)) ∧ (∃ y : ((y ∈ A) ∧ (y ∉ B)))). An improper superset of S contains every element of S and may or may not contain more elements, a proper superset of S contains every element of S and at least one more. The term 'superset' (without a qualifier) means either type, which really means the same thing as improper superset (since every proper superset is also an improper one).