The process in which a relatively unspecialized monocyte acquires the specialized features of an osteoclast. An osteoclast is a specialized phagocytic cell associated with the absorption and removal of the mineralized matrix of bone tissue. [ http://www.ncbi.nlm.nih.gov/pubmed/12161749 http://purl.obolibrary.org/obo/CL_0000092 GOC:add http://openisbn.com/search.php?q=0781735149&isbn=1/ ]