Main form: centre or centre, noun.
Other forms: central (adjective), center/centre (verb)
- Something right in the middle, such as the center of a circle.
- Something pivotal, crucial, a key ingredient.
- A basin of attraction, something to which things get drawn.
- The average.
- In the middle, a compromise position, typically use for ideologies or viewpoints.
- A source or point of origin, typically for something transmitted in all directions, such as light.
- A facility providing a service.
Typically used for an element or a subset in a set with additional structure, satisfying certain special core properties.
In group theory
Center of a group: The set of those elements of the group that commute with every element of the group. It forms a subgroup, in fact, a characteristic subgroup.
Primary subject wiki entry: Groupprops:Center
Also located at: Wikipedia:Center (group theory)
In ring theory
Center of a ring: The set of those elements of a (usually unital) ring that commute with every element of the ring. The center of a ring is a subring; for a unital ring, it is a subring containing the multiplicative identity.
Primary subject wiki entry: Noncommutative:Center of a ring