Hema

• "Hema" and "hemo" refer to the blood. Hematology is the study of blood, and hematuria is the presence of blood in the urine, according to FamilyDoctor.org.
  
  

Poly

• "Poly," in medicine, refers to the excess of something. Polydactyly is an excess number of fingers or toes, and polydipsia is an excessive thirst.
  
  

Psych

• The prefix "psych" refers to the mind and mental processes. Psychiatry is the study and treatment of mental disorders, according to FamilyDoctor.org, and the term "psychopath" refers to someone with a mental illness characterized by a lack of empathy for others.
  
  

Tachy

• Medical definitions involving rapidity start with "tachy." Tachycardia is a rapid heartbeat, while tachypnea refers to rapid breathing.
  
  

Bact

• The prefix "bact" refers to bacteria. Bacteremia is bacteria in the blood, and bacteriuria is the presence of bacteria in the urine.