Library
▹
Essentials
▹
Relations
Definition 1.4.9.
Let
S
be a set,
⪯
be a
relation
on
S
. We define:
⪯
is reflexive
:
⇔
∀
s
∈
S
:
s
⪯
s
References.
https://en.wikipedia.org/wiki/Reflexive_relation
https://mathworld.wolfram.com/Reflexive.html
https://proofwiki.org/wiki/Definition:Reflexive_Relation
https://ncatlab.org/nlab/show/reflexive+relation
https://coq.inria.fr/library/Coq.Sets.Relations_1.html#Reflexive
https://leanprover-community.github.io/mathlib_docs/init/logic.html#reflexive