A pinnacle (from Latinpinnaculum, a little feather, pinna, compare panache) is an architectural ornament originally forming the cap or crown of a buttress or small turret, but afterwards used on at the corners of and in many other situations. The pinnacle looks like a small spire. It was mainly used in Gothic architecture.
In mathematics, especially in set theory, a setA is a subset of a set B, or equivalently B is a superset of A, if A is "contained" inside B, that is, all elements of A are also elements of B. A and B may coincide. The relationship of one set being a subset of another is called inclusion or sometimes containment.
