Haematology – The scientific study of blood
We know that ology is "the study of" (see ology)
Haema = blood, which can be remembered from:
He decided he must (haema) give blood every week.
So, haematology must mean the study of blood.
Examples of haematology in a sentence
He went to university to study haematology.
The doctor couldn't figure out what was wrong with her, so he sent her to the haematology clinic to see a specialist.
She stopped by the haematology lab to see whether her patient's blood tests were done.