Directed Sets
In a totally ordered set, the terms maximal element and greatest element coincide, which is why both terms are used interchangeably in fields like analysis where only total orders are considered. This observation does not only apply to totally ordered subsets of any poset, but also to their order theoretic generalization via directed sets. In a directed set, every pair of elements (particularly pairs of incomparable elements) has a common upper bound within the set. It is easy to see that any maximal element of such a subset will be unique (unlike in a poset). Furthermore, this unique maximal element will also be the greatest element.
Similar conclusions are true for minimal elements.
Further introductory information is found in the article on order theory.
Read more about this topic: Maximal Element
Famous quotes containing the words directed and/or sets:
“Apart from letters, it is the vulgar custom of the moment to deride the thinkers of the Victorian and Edwardian eras; yet there has not been, in all history, another age ... when so much sheer mental energy was directed toward creating a fairer social order.”
—Ellen Glasgow (1873–1945)
“There is a small steam engine in his brain which not only sets the cerebral mass in motion, but keeps the owner in hot water.”
—Unknown. New York Weekly Mirror (July 5, 1845)