Definition:Containment

Disambiguation

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Containment may refer to:

• 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 solid geometric figure: a solid figure is intuitively described as beingcontained by the surfaces that form its boundary.
  • Containment of a rectangle: In Euclid's The Elements, 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 $T$ 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.