When studying and using medical terminology it is important to understand the basic structure of medical terms and their meanings. In medicine, all parts of a medical term are essential to the overall meaning of the phrase.

When learning about language and medical terminology, remember that words contain patterns.  The more you read and become familiar with medical terminology, the easier it will be to understand and use the terms. While many words are clear derivatives of a set term, others do not always follow the same patterns..

Medical terms usually consist of three parts - a root, a prefix and a suffix. When the three are combined it will express the meaning of the term. These types of words are called constructed words as they usually contain all three elements i.e. prefix, root and suffix. For example:


MYO + CARDI + AL =  muscle + heart + ‘of’ =  of the heart muscle

Prefix    root      Suffix

The root of a word (known as the word root) contains the basic meaning (definition) of the word often referring to a body part or system. In this case, myocardial means ‘of the heart muscle’. This word is commonly used in phrases like ‘myocardial infarction’ – where an ‘infarction’ is an obstruction of a blood vessel which is causing the death of the surrounding tissue. ‘Myocardial infarction’ means this obstruction has taken place in the heart muscle – and a heart attack has occurred.


There may be more than one word root in a medical term. These are often combined with an additional vowel to make them easier to pronounce.


CARDI + O + PULMONARY = heart and lungs

A prefix may or may not be present. Where it is used, a prefix is placed in front of the word to change its meaning or to identify the core meaning of the word. A prefix added to ‘cardi’ (heart) will identify the type of heart condition. For example:


DEXTRO + CARDI + A = right + heart


Dextrocardia means the heart is on the right side of the body, instead of the more common left side.

The prefixes ‘a’ or ‘an’ mean ‘without’ and are frequently used in medical terminology. For example


AN + AEMIA = without blood


(anaemia involves a lack of iron within the blood. A person with anaemia lacks the full oxygen carrying capacity of red blood cells. They appear to lack blood)



AN + OREXIA = without appetite


(anorexia is an eating disorder that involves the person refusing to eat)

A prefix may also indicate a time, place, location or status. For example,


INTRA + VEN + OUS = within + veins + full of


This term translates as ‘within the (full) veins’ – and is commonly used when talking about providing plasma, medications or blood to a patient. The liquid is supplied directly into the veins.

A suffix is found after the word root(s) and can also change the meaning or function of the word root. A suffix can modify the root word’s form, changing it from a noun to a verb or adjective.  The suffix could also refer to a condition, disorder, or medical procedure to treat it. For example,


ARTHR+ ITIS = bone + inflammation or inflammation of the joints




APPEND + ECTOMY = surgical removal of the appendix


Combining vowels can also be used to join two root words and indicate a location. For example,


PNEUM + O + THORAX = air, lungs and gas + chest cavity = abnormal air or gas in the cavity surrounding the lungs

Some medical terms contain only a prefix and a suffix without a root word, or they contain two root words that are bound together by a combining vowel (often an ‘o’). For example,


CARDI + O + VASCULAR = the heart and all blood vessels


CARDI + O + TOMY = a surgical incision into the heart muscle


The ‘o’, or any combining vowel, does not have a meaning, it is used to combine the two words and make them easier to pronounce.

Medical terms may also consist of only a prefix and suffix along with a combining vowel:


A + PNOEA = without breathing (sleep apnoea means a person stops breathing momentarily while they are sleeping)

Constructed words are easy to break down and understand when you learn the meanings of each part of the word.


Some medical words are not constructed from the suffix, root and prefix combination. These words are known as non-constructed medical terms. Non-constructed terms cannot be deconstructed into their individual word part so you must memorise them in their totality. They are usually words derived from other languages (particularly Latin or Greek), acronyms or abbreviations they also include eponyms (medical terms named after the person who discovered the medical condition or procedure).

Learn more with our Medical Terminology Course.