Description: Value of join for subsets of Hilbert space in terms of supremum: the join is the supremum of its two arguments. Based on the definition of join in Beran p. 3. For later convenience we prove a general version that works for any subset of Hilbert space, not just the elements of the lattice CH . (Contributed by NM, 2-Mar-2004) (Revised by Mario Carneiro, 23-Dec-2013) (New usage is discouraged.)