In ring theory, combinatorics, functional analysis, and theoretical computer science, a semifield is a semiring (MSC 16Y60) (S,+,ยท) in which all elements have a multiplicative inverse.
•
In projective geometry and finite geometry (MSC 51A, 51E, 12K10), a semifield is the analogue of a division algebra, but defined over the integers Z rather than over a field.