The article is dedicated to medical terminology problems (synonimy, polysemy, eponymy etc.). Special attention is paid to the medical terms history, classification, etymology, semantics and structure. Manners of terms creation, terminological upside-downs, causes and consequences of terminological “epidemics” are considered. The professional terminology unification and consistency importance for the medical science improvement is stressed. The importance of the terms being accurate and definite as an obligatory condition of the efficient medical workers and scientists communication is stated.