Join

In a lattice, any two elements a and b have a least upper bound. This least upper bound is often called the join of a and b, and is denoted by a v b.

One can also speak of the join operation in a general partially ordered set. If a and b are two elements in some partially ordered set (A,<=), and if there is a smallest element (with respect to the given order) c with the property that a<=c and b<=c, then c is said to be the join of a and b.