Introduction to Medical Terminology
Medical terminology is language used to describe anatomical structures, procedures, conditions, processes, and treatments. At first glance, medical terms may appear intimidating, but once you understand the basic word structure and the definitions of some common word elements, the meaning of thousands of medical terms can be easily parsed.
Most medical terms adhere to a fixed structure of a prefix, root, and suffix. These word 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. English is used in most influential medical journals and it has become the language of choice at international conferences.2
Basic Term Structure
Medical terms are comprised of these standard word parts:
- Prefix: When included, the prefix appears at the beginning of a medical term and usually indicates a location, direction, type, quality, or quantity.
- Root: The root gives a 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 a term and may indicate a specialty, test, procedure, function, disorder, or status. Otherwise, it may simply define whether the word is a noun, verb, 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 into its component parts should help readers determine the meaning of an unfamiliar term. For example, hypothermia has the prefix hypo- (meaning below normal), the root therm (heat or warmth), and the suffix -ia (condition).
A root is the foundational element of any medical term. Roots often indicate a body part or system.
Common word roots:
|Heart and Circulatory|
|Bones and Muscles|
|intestine (usually small)||enter|
|Other Common Roots|
A medical word may include multiple roots. This frequently occurs when referencing more than one body part or system. For example, cardio-pulmo-nary means pertaining to the heart and lungs; gastro-entero-logy means the study of the stomach and intestines.
A combining vowel is used when a root is followed by another word part that begins with a consonant. A combining vowel (usually the letter ‘o’) is added after the root (e.g. neur-o-logy) to aid pronunciation. The root and vowel together (e.g. neur-o) are called the combining form. For simplicity, combining vowel options are omitted from the 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.
|half (one side)||hemi-|
|two | three | four||bi- | tri- | quad(ri)-|
|Time or Speed|
|before||pro-, pre-, ante-|
|time, long time||chron-|
|Location or Relationship|
|out of, outside||ex-, ec(t)-|
|Function or Quality|
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 make the word a noun or adjective. For example, the endings -a, -e, -um, and -us are commonly used to create 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).
Common suffixes (letters in parenthesis are not always present):
|Basic Noun and Adjective Suffixes|
|(noun form)||-a, -e, -um, -is|
|condition||-ia, -ism, -sis, -y|
|specialty||-iatry, -iatrics, -ics|
|pertaining to||-ac, -ar(y), -(e/i)al, -ic(al), -ior, -ory,, -ous, -tic|
|Tests and Procedures|
|Pathology or Function|
|blood (condition of)||-emia|
|condition or disease||-osis|
Adding an “s” or “es” to the end of a word is often the straightforward method to make a word plural 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.
There are several exceptions. For example, “virus” is a Latin term without a plural form. “Viruses” is the accepted plural form. Elsewhere, the suffix “s” or “es” has occasionally prevailed in common usage. For example, the plural form of “hematoma” is “hematomas” rather than “hematomata.”
Common singular endings and corresponding plural endings:
|ex, ix, yx||ices|
- OpenMD Medical Dictionary and word parts glossary, which provides definitions for 750 medical roots, prefixes, and suffixes.
- Understanding Medical Words by MedlinePlus provides a concise introduction to medical terminology and several quizzes.
- TheFreeDictionary's Medical Dictionary by Farlex is a comprehensive dictionary of medical terms (including word parts) from American Heritage, Collins Encyclopedia, and other major publishers.
- Banay, G L. “An Introduction to Medical Terminology I. Greek and Latin Derivations.” Bulletin of the Medical Library Association vol. 36, 1 (1948).
- Wulff, Henrik R. “The language of medicine.” Journal of the Royal Society of Medicine vol. 97,4 (2004): 187-8.
- Ehrlich, Ann; Schroeder, Carol L. Introduction to Medical Terminology. Centage Learning, 2015.
- Nath, Judi Lindsley; Lindsley, Kelsey P. A Short Course in Medical Terminology. Wolters Kluwer Health, 2018.
- 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
Last updated: December 24, 2021