tmp goto 경계,bound
greatest lower bound = 최대하계 = 하한 = infimum → 하한,infimum
하계(lower bound)가 존재하면 그 집합은 "bounded from below"라고 한다.
https://mathworld.wolfram.com/BoundedfromBelow.html
cf. from을 뺀
https://proofwiki.org/wiki/Definition:Bounded_Below
https://mathworld.wolfram.com/BoundedfromBelow.html
cf. from을 뺀
https://proofwiki.org/wiki/Definition:Bounded_Below
Compare: 상계,upper_bound