Variety (universal algebra)In universal algebra, a variety of algebras or equational class is the class of all algebraic structures of a given signature satisfying a given set of identities. For example, the groups form a variety of algebras, as do the abelian groups, the rings, the monoids etc. According to Birkhoff's theorem, a class of algebraic structures of the same signature is a variety if and only if it is closed under the taking of homomorphic images, subalgebras, and (direct) products.
Lotus SoftwareLotus Software (called Lotus Development Corporation before its acquisition by IBM) was an American software company based in Massachusetts; it was "offloaded" to India's HCL Technologies in 2018. Lotus is most commonly known for the Lotus 1-2-3 spreadsheet application, the first feature-heavy, user-friendly, reliable, and WYSIWYG-enabled product to become widely available in the early days of the IBM PC, when there was no graphical user interface.
Product bundlingIn marketing, product bundling is offering several products or services for sale as one combined product or service package. It is a common feature in many imperfectly competitive product and service markets. Industries engaged in the practice include telecommunications services, financial services, health care, information, and consumer electronics. A software bundle might include a word processor, spreadsheet, and presentation program into a single office suite.
Upper setIn mathematics, an upper set (also called an upward closed set, an upset, or an isotone set in X) of a partially ordered set is a subset with the following property: if s is in S and if x in X is larger than s (that is, if ), then x is in S. In other words, this means that any x element of X that is to some element of S is necessarily also an element of S. The term lower set (also called a downward closed set, down set, decreasing set, initial segment, or semi-ideal) is defined similarly as being a subset S of X with the property that any element x of X that is to some element of S is necessarily also an element of S.
