Introduction to Medical Terminology

Medical terminology is language used to describe anatomical structures, procedures, conditions, processes, and treatments. It may seem intimidating at first glance. However, once the structure is understood and the definitions of some common word elements are memorized, the meaning of thousands of medical terms can be parsed.

Most medical terms adhere to a fixed structure of a prefix, root, and suffix using a standard set of word elements. These common components are assembled like building blocks to create a vast vocabulary.

Greeks are considered the founders of rational medicine and medical terms are primarily derived from Greek and Latin.1 Over centuries, the language of medicine has evolved into multiple national medical languages. Today, medical English is the dominant language for international communication. Most influential medical journals are written in English and it has become the language of choice at international conferences.2

Basic Structure

Medical terms are comprised of these standard word parts:

  • Prefix: When present, the prefix appears at the beginning of the medical term. It usually indicates a location, direction, type, quality, or quantity.
  • Root: A root gives the term its essential meaning. Nearly all medical terms contain at least one root. When a prefix is absent, the term begins with a root.
  • Suffix: The suffix appears at the end of the term and may indicate a specialty, test, procedure, function, disorder, or status. Alternatively, it may just turn the word into a noun or adjective.
  • Combining Vowel: A combining vowel (usually the letter “o”) may be added between word parts to aid in pronunciation.

Breaking a word down to its component parts should help you to determine the meaning of an unfamiliar term. For example, hyperglycemia has the prefix hyper- (above normal), root glyc (glucose/sugar), and suffix -emia (in blood). The term means high blood sugar level.

Word Roots

A root is the foundational element of the word that defines the basic meaning. Roots often indicate a body part or system.

Here are some common roots:

brain enceph
ear ot
eardrum tympan, myringo
eye ophthalm, ocul
face faci
nose rhin
skull cran
tongue lingu
tooth odont, dent
Heart and Circulatory
aorta aort
arteries arteri
blood hem, sangu
blood vessels angi
heart cardi
veins ven, phleb
Bones and Muscles
muscles myo
shoulder scapul
arm brachi
wrist carp
rib cost
back dorsa
bones oste
foot pod, ped
Other Common Roots
knowledge gnos
life bi
pressure bar
drug chem
electric electr
returned sound echo

Compound Words

When referencing more than one body part or system, a medical word may include multiple roots. For example, cardio-pulmo-nary means pertaining to the heart and lungs; gastro-entero-logy means the study of the stomach and intestines.

Combining Forms

When a word part is followed by another part that begins with a consonant, a combining vowel (usually the letter ‘o’) is added after the root (e.g. cardi-o-logy) to aid pronunciation. The root and vowel together (e.g. cardi-o) are referred to as the combining form. For simplicity, we have omitted combining vowel options from word part tables.


A prefix modifies the meaning of the word root. It may indicate a location, type, quality, body category, or quantity. The prefix is optional and does not appear in all medical terms.

Here are some common prefixes:

large macro-, mega(lo)-
small micro-
half semi-
half (one side) hemi-
one mono-, uni-
two | three | four bi- | tri- | qua(dr/r/t)-
equal equi-
many poly-
Level or Speed
above normal hyper-
below normal hypo-
fast tachy-
slow brady-
Location or Relationship
away from ab-
above supra-
around peri-
across trans-
between inter-
out of, outside ex-, ec(t)-
through, completely dia-
together con-
toward ad-
within, inside end(o)-
Function or Quality
against anti-, contra-
bad mal-
cause eti-
self auto-
without a-, de-
not working correctly dys-


Medical terms always end with a suffix.3 The suffix usually indicates a specialty, test, procedure, function, condition/disorder, or status. For example, “itis” means inflammation and “ectomy” means removal.

Alternatively, the suffix may simply turn the word into a noun or adjective. The endings -a, -e, -um, and -us are commonly used to turn a word into a singular noun (e.g. crani-um).

Though the suffix appears at the end of the term, it often comes first in the definition. “For example, appendicitis means: inflammation (-itis) of the appendix.”4 Accordingly, it is sometimes helpful to read unfamiliar medical terms from right to left.

Occasionally, a medical term may be comprised of a prefix and suffix. For example, apnea includes the prefix a- (without) and suffix -pnea (breathing).

Here are some common suffixes:

Basic Noun and Adjective Suffixes
(noun form) -a, -e, -um, -is
causing -genic
condition -ia, -ism, -sis, -y
specialty -iatry, -iatrics, -ics
specialist -ian, -ist
structure -um, -us
study of -logy
pertaining to -ac, -ar(y), -(e/i)al, -ic(al), -ior, -ory,, -ous, -tic
Tests and Procedures
removal of -ectomy
image/recording -gram
making a picture -graph(y)
cut in -otomy
viewing -scopy
opening -stomy
Pathology or Function
blood condition -emia
breathing -pnea
inflammation -itis
condition or disease -osis
deficiency -penia
disease -pathy
excessive flow -rrhag(e/ia)

Plural Forms

Adding the suffix “s” (or “es”) to a word is often the straightforward method used to create the plural form in English and many modern Romance languages. In medical terminology, however, things are a little more complicated. The plural form of each word is based on the last two letters of the singular suffix. The table below shows suffix endings and corresponding plural endings.

There are several exceptions. For example, virus is a Latin term without a plural form, so its plural is “viruses.” Elsewhere, the suffix -(e)s has prevailed in common usage. For example, the plural form of “hematoma” is “hematomas” rather than “hematomata.”

Plural Forms5
(singular ending) (plural ending)
a ae
en ina
ex, ix, yx ices
is es
ma mata
(a/i/y)nx nges
um a
us i(i)

Additional resources:

  • The Understanding Medical Words Tutorial by MedlinePlus provides an introductory tutorial on forming medical words.
  • For an expanded list of medical word components, visit Word Parts and What They Mean at MedlinePlus.
  • TheFreeDictionary's Medical Dictionary by Farlex offers a comprehensive dictionary of medical terms (including word parts) from American Heritage, Collins Encyclopedia, and other major publishers.


  1. Banay, G L. “An Introduction to Medical Terminology I. Greek and Latin Derivations.” Bulletin of the Medical Library Association vol. 36, 1 (1948).
  2. Wulff, Henrik R. “The language of medicine.” Journal of the Royal Society of Medicine vol. 97,4 (2004): 187-8.
  3. Ehrlich, Ann; Schroeder, Carol L. Introduction to Medical Terminology. Centage Learning, 2015.
  4. Nath, Judi Lindsley; Lindsley, Kelsey P. A Short Course in Medical Terminology. Wolters Kluwer Health, 2018.
  5. Cohen, Barbara J. Medical Terminology: An Illustrated Guide. 6th ed. Baltimore, MD: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2011. Table 2-4.

Published: January 9, 2020