Centre of a ring
The collection of all elements of the ring that commute with every element, that is,
The centre of a ring is a subring containing together with every invertible element its inverse. The centre of a ring that is an algebra with a unit element over a field contains the ground field (see Central algebra).
Centre of a ring. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Centre_of_a_ring&oldid=18869