haematology UK /ˌhiːməˈtɒlədʒi/US /ˌhiməˈtɑləd͡ʒi/ noun2 •The scientific study of blood and blood-producing organs.‘Mr Carter, will you remind me again how long you’ve specialised in haematology?’ — 2014 •The medical specialty dealing with the health and diseases of blood and blood-producing organs.