1.6 Prefixes

A prefix is located at the beginning of a medical term and alters the meaning of the term. It is important to spell and pronounce prefixes correctly. When writing a prefix, if it is not in a medical term, you must place a “-” after the prefix. Not all medical terms have a prefix, but many do.

The following is a good technique to help you memorize prefixes:

  • Start by reviewing the most common prefixes. We will look at more prefixes in Chapter 3.
  • Compare the prefixes to the examples of use in medical terms in the tables below.
  • Try to relate the prefixes below to common terms you hear in everyday life.


Table 1.11. Prefixes 

a- , an- no, not anemia
aut- self autopsy
dia- complete, through diagnosis
dys- bad, painful, difficult, abnormal dyspnea
endo- within endoscope
exo- outside exocrine 
hyper- too much, excessive hypertension
hypo- too little, less than normal hypotension
intra- within intravenous


Key Concept

The following is a list of some common anemias:

Aplastic anemia: A condition in which the body does not produce enough red blood cells

Thalassemia: An inherited disorder in which the body does not produce enough hemoglobin

Sickle cell anemia: An inherited disorder where the red blood cells are crescent-shaped; Fig. 1.19 below shows the difference between healthy red blood cells and the crescent-shaped red blood cells that occur with sickle cell anemia

Vitamin deficiency anemia or pernicious anemia: A condition in which the body lacks vitamin B12, which is required to produce red blood cells

Iron deficiency anemia: A condition in which the body lacks iron, which is carried on the red blood cells and allows the red blood cells to carry oxygen

Hemolytic anemia: A condition that can either be inherited or develop later in life and is caused by the body destroying red blood cells faster than they can be produced

(Mayo Clinic, 2022)


Red blood cells and sickle cells
Fig. 1.19
body with symptoms of anemia
Fig. 1.18

Key Concept

Simply changing the prefix can change the meaning of a medical term entirely.

The prefixes hyper- and hypo- are used in many medical terms and usually mean the opposite of each other. See the examples below:

  • hypertension (high blood pressure) and hypotension (low blood pressure)
  • hyperthyroidism (condition of high thyroid) and hypothyroidism (condition of low thyroid)
  • hyperglycemia (high blood sugar) and hypoglycemia (low blood sugar)


Table 1.12. Prefixes

peri- surrounding pericardium
pro- before, forward prognosis
re- back resection
retro- behind retroperitoneal 
sub- below, under subhepatic
trans- across, through transdermal


image of pericardial sac
Fig. 1.20

Key Concept

The pericardium (Fig. 1.20) surrounds the heart. Its function is to protect, lubricate, and keep the heart in the correct position in the chest cavity (Healthline, 2022). The term can be broken down as follows: peri- (“surrounding”), cardi (“heart”), and -um (“structure”), which gives you “a structure surrounding the heart.”






Unless otherwise indicated, material on this page has been adapted from the following resource:

Carter, K., & Rutherford, M. (2020). Building a medical terminology foundation. eCampusOntario. https://ecampusontario.pressbooks.pub/medicalterminology/ licensed under CC BY 4.0



Healthline. (2022). Pericardium. https://www.healthline.com/health/pericardium

Mayo Clinic. (2022). Anemia. https://www.mayoclinic.org/diseases-conditions/anemia/symptoms-causes/syc-20351360


Image Credits
(Images are listed in order of appearance)

Symptoms of anemia by Mikael Häggström, Public domain

Sickle cell anemia by Pkleong, Public domain

Blausen 0724 PericardialSac by Blausen Medical Communications, Inc., CC BY 3.0



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The Language of Medical Terminology Copyright © 2022 by Lisa Sturdy and Susanne Erickson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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