In a lattice, any two elements 
and 
have a least upper bound. This least upper bound is often called the join of 
and 
, and is denoted by 
.
One can also speak of the join operation in a general partially ordered set. If 
and 
are two elements in some partially ordered set 
, and if there is a smallest element (with respect
to the given order) 
with the property that 
and 
, then 
is said to be the join of 
and 
.
