Explore Set on MathWorld

In mathematics, a set is a finite or infinite collection of objects in which order has no significance and multiplicity is generally also ignored.

Set is a middle school-level concept.


Closed Set: A closed set is a subset of a topological space that contains all of its limit points. A closed interval is an example of a closed set.
Open Set: An open set is a set for which every point in the set has a neighborhood lying in the set. An open set is the complement of a closed set and. An open interval is an example of an open set.
Subset: A subset is a portion of a set. Subsets can also consist of the entire set or be empty.

Classroom Articles on Pre-Algebra (Up to Middle School Level)

  • Absolute Value
  • Least Common Multiple
  • Arithmetic
  • Line
  • Arithmetic Series
  • Origin
  • Associative
  • Polynomial
  • Base
  • Power
  • Cartesian Coordinates
  • Prime Factor
  • Commutative
  • Prime Factorization
  • Decimal Expansion
  • Prime Number
  • Distributive
  • Pythagorean Theorem
  • Divisor
  • Quotient
  • Equal
  • Real Line
  • Factorial
  • Real Number
  • Fraction
  • Relatively Prime
  • Function Graph
  • Right Angle
  • Geometric Series
  • Rounding
  • Greatest Common Divisor
  • Sequence
  • Integer
  • Series
  • Intersection
  • Square Number
  • Interval
  • Square Root
  • Irrational Number