osteoporosis

Concise Oxford English Dictionary © 2008 Oxford University Press:
osteoporosis /ˌɒstɪəʊpəˈrəʊsɪs/

▶noun a medical condition in which the bones become brittle from loss of tissue, typically due to hormonal changes, or deficiency of calcium or vitamin D.

– derivatives
osteoporotic adjective.

– origin C19: from osteo- + Gk poros ‘passage, pore’ + -osis.