Linked from
The 8 pages that link to Upper bound, each with the reason it gives.
SupremumRelated: A supremum must first be an upper bound of the set.
Lattice (order theory)Related: The least upper bound in a lattice is the join of the subset's pair.
Zorn's lemmaRelated: Each chain must have an upper bound in the partially ordered set.
Infimum and supremumRelated: A supremum is the least element among a set's upper bounds.
Join and meetRelated: A join is the least element among the upper bounds.