2. In medical and pathological terminology, hydro- is extensively used to form names of diseases (chiefly in Latin or Greek form), being prefixed (a) to names of parts of the body, to denote that such part is dropsical or affected with an accumulation of serous fluid, as in hydroabdomen (dropsy of the abdomen, ascites), hydroblepharon (-um) [Greek βλέϕαρον eyelid] , hydrocardia [Greek καρδία heart] , hydrocranium, hydroderma, hydrogaster [Greek γαστήρ belly] , hydrogastria, hydrohystera [Greek ὑστέρα womb] , hydromphalum (-us) [Greek ὀμϕαλός navel] , hydromyelus, hydromyelia [Greek μυελός marrow, used for ‘spinal cord’] , hydronephros [Greek νεϕρός kidney] , hydro-ovarium [see ovary n.] , hydropericardium, hydroperitonaeum, hydrorrhachis [Greek ῥάχις spine] , hydrosalpinx [Greek σάλπιγξ trumpet, used for ‘Fallopian tube’] , hydrothorax; also, in the combination hydropneumo-, to express the presence of water and air, as in hydropneumopericardium, hydropneumothorax; (b) to names of diseases or diseased formations, denoting the accompaniment of dropsy or of an accumulation of serous fluid, as hydrocachexia, -y [see cachexy n.] , hydrodiarrhœa, hydrohaemothorax, hydromeningitis, hydropericarditis, hydroperitonitis, hydrorrhachitis, etc.; hydrocirsocele, hydr(o)enterocele, hydromeningocele, hydromyelocele, hydrophysocele, hydrosarcocele, hydroscheocele, etc.