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. [ https://www.worldcat.org/search?q=bn%3A0781735149 GOC:add http://purl.obolibrary.org/obo/CL_0000092 http://www.ncbi.nlm.nih.gov/pubmed/12161749 ]