Definition:Containment


 * Geometry
 * Containment of an angle: The two lines that form an angle are said to contain that angle.
 * Containment of a geometric figure: a figure is intuitively described as being contained by its boundary.
 * Containment of a rectangle: In Euclid's, two adjacent sides of a rectangle are said to contain it.


 * In set theory, the concept of containment can be used in either of two senses:
 * A set is said to contain its elements: $S$ contains $a$ means $a \in S$.
 * A set is said to contain its subsets: $S$ contains $$ means $T \subseteq S$.
 * Consequent to this ambiguity, it is strongly advised that the term contain is not used.

Also see

 * Definition:Jordan Curve, for a rigorous definition of the concept of containment in the complex plane.