In algebraic geometry, a regular scheme is a locally Noetherian scheme whose local rings are regular everywhere. Every smooth scheme is regular, and every regular scheme of finite type over a perfect field is smooth.
For an example of a regular scheme that is not smooth, see Geometrically regular ring § Examples.
See also
References
Hartshorne, Robin (1977), Algebraic Geometry, Graduate Texts in Mathematics, vol. 52, Springer, p. 238, ISBN 9780387902449. Note that the cited definition that Hartshorne gives is slightly misleading. A locally Noetherian scheme is regular if all its local rings are regular, but it is not the case for schemes which are not locally Noetherian. See the cited Stacks Project page for more details. 9780387902449 ↩
"Section 28.9 (02IR): Regular schemes". stacks.math.columbia.edu. The Stacks project. Retrieved 2022-02-18. https://stacks.math.columbia.edu/tag/02IR ↩
Demazure, Michel (1980), Introduction to algebraic geometry and algebraic groups, North-Holland Mathematics Studies, vol. 39, North-Holland, Proposition 3.2, p. 168, ISBN 9780080871509. 9780080871509 ↩