Noun
(mathematics) A nonempty subset of a lattice.
(mineralogy) Any of several independent lattices present in a crystal.
Source: en.wiktionary.orgComplete sublattices A sublattice M of a complete lattice L is called a complete sublattice of L if for every subset A of M the elements A and A, as defined in L, are actually in M. Burris, Stanley N., and H.P. Sankappanavar, H. P., 1981. Source: Internet
If the above requirement is lessened to require only non-empty meet and joins to be in L, the sublattice M is called a closed sublattice of M. Examples * Any non-empty finite lattice is trivially complete. Source: Internet