Medical Terminology
The prefixes, roots and suffixes medical words are built from, searchable with worked examples.
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| Word part | Meaning | Example |
|---|---|---|
| a-, an- | Without, absence of | anaemia |
| brady- | Slow | bradycardia |
| tachy- | Fast | tachycardia |
| hyper- | Above normal, excessive | hypertension |
| hypo- | Below normal, deficient | hypoglycaemia |
| dys- | Difficult, painful, abnormal | dysphagia |
| eu- | Normal, good | euthyroid |
| peri- | Around | pericardium |
| endo- | Within, inner | endoscopy |
| epi- | Upon, over | epidermis |
| inter- | Between | intercostal |
| intra- | Within | intravenous |
| sub- | Under, below | subcutaneous |
| supra- | Above | suprapubic |
| poly- | Many, much | polyuria |
| olig-, oligo- | Few, scanty | oliguria |
| pre- | Before | preoperative |
| post- | After | postpartum |
| macro- | Large | macrocytic |
| micro- | Small | microcephaly |
| para- | Beside, near, abnormal | paranasal |
| trans- | Across, through | transdermal |
| anti- | Against | antipyretic |
| neo- | New | neonatal |
| cardi/o | Heart | carditis |
| derm/o, dermat/o | Skin | dermatology |
| gastr/o | Stomach | gastritis |
| enter/o | Intestine | gastroenteritis |
| hepat/o | Liver | hepatomegaly |
| nephr/o, ren/o | Kidney | nephrectomy |
| neur/o | Nerve | neuropathy |
| oste/o | Bone | osteoporosis |
| my/o | Muscle | myalgia |
| arthr/o | Joint | arthroscopy |
| haem/o, haemat/o | Blood | haematuria |
| angi/o, vas/o | Vessel | angioplasty |
| phleb/o, ven/o | Vein | phlebotomy |
| pneum/o, pulmon/o | Lung, air | pneumonia |
| thorac/o | Chest | thoracotomy |
| encephal/o | Brain | encephalitis |
| cyst/o | Bladder, sac | cystoscopy |
| col/o, colon/o | Colon | colonoscopy |
| hyster/o | Uterus | hysterectomy |
| mast/o | Breast | mastectomy |
| ot/o | Ear | otitis |
| ophthalm/o | Eye | ophthalmology |
| rhin/o | Nose | rhinoplasty |
| cyt/o | Cell | cytology |
| path/o | Disease | pathology |
| psych/o | Mind | psychiatry |
| lapar/o | Abdomen, abdominal wall | laparoscopy |
| -algia | Pain | neuralgia |
| -itis | Inflammation | appendicitis |
| -ectomy | Surgical removal | tonsillectomy |
| -otomy, -tomy | Surgical incision | tracheotomy |
| -ostomy, -stomy | Surgical opening | colostomy |
| -plasty | Surgical repair | arthroplasty |
| -scopy | Visual examination | endoscopy |
| -graphy | Process of recording | radiography |
| -gram | The record produced | electrocardiogram |
| -ology | Study of | cardiology |
| -oma | Tumour, mass | carcinoma |
| -osis | Abnormal condition | fibrosis |
| -pathy | Disease | cardiomyopathy |
| -megaly | Enlargement | splenomegaly |
| -penia | Deficiency | thrombocytopenia |
| -aemia, -emia | Blood condition | hyperkalaemia |
| -uria | Urine condition | proteinuria |
| -rrhoea, -rrhea | Flow, discharge | rhinorrhoea |
| -rrhage, -rrhagia | Bursting forth, bleeding | haemorrhage |
| -sclerosis | Hardening | atherosclerosis |
| -stenosis | Narrowing | aortic stenosis |
| -lysis | Breakdown, destruction | haemolysis |
| -cyte | Cell | leucocyte |
| -oid | Resembling | lipoid |
Roots are written with the combining vowel that joins them to the next part, usually o — cardi/o. The vowel is kept before a part starting with a consonant (cardiology) and dropped before one starting with a vowel (carditis). Spellings here follow British usage where it differs; American texts write haem- as hem- and -rrhoea as -rrhea.
Medical words are assembled from parts rather than invented, so most can be decoded on sight. Split the term into prefix, root and suffix and read it backwards: bradycardia is brady- (slow) + cardi/o (heart) + -ia (condition) — a slow heart rate.
Three slots, read back to front
Almost every clinical term fits the same pattern. A root names what the word is about, usually a body part. A prefix in front modifies it — position, number, timing or degree. A suffix at the end says what is happening: a condition, a procedure, a state. The trick is that the meaning reads from the suffix backwards, not left to right.
So gastroenteritis is not read as “stomach, intestine, inflammation” but as “inflammation of the stomach and intestine”. Once that habit is in place, a term never seen before becomes a small puzzle with a reliable answer rather than a word to look up.
The combining vowel
Roots are listed with a slash and a vowel — cardi/o, gastr/o — because they need a linking vowel to join the next part smoothly. The rule is short: keep the vowel before a part that begins with a consonant, drop it before one that begins with a vowel. That is why it is cardiology but carditis, and gastroscopy but gastrectomy.
- 1 Find the suffix. In pericarditis the ending is -itis, which means inflammation.
- 2 Find the root. The middle is cardi, the heart.
- 3 Find the prefix, if there is one. The front is peri-, meaning around.
- 4 Read from the suffix back to the front. Inflammation — of the area around — the heart: inflammation of the pericardium.
- 5 Check it against the combining vowel. The o of cardi/o is dropped because -itis begins with a vowel, which confirms the split is right.
The same root through several suffixes
One root, five meanings — which is why learning the suffixes pays off fastest.
| Term | Parts | Means |
|---|---|---|
| Cardiology | cardi/o + -ology | The study of the heart |
| Carditis | cardi + -itis | Inflammation of the heart |
| Cardiomegaly | cardi/o + -megaly | Enlargement of the heart |
| Cardiomyopathy | cardi/o + my/o + -pathy | Disease of the heart muscle |
| Electrocardiogram | electr/o + cardi/o + -gram | A record of the heart’s electrical activity |
Pairs that are easy to confuse
Each pair differs by one or two letters and by a great deal of meaning.
| Pair | Difference |
|---|---|
| -otomy vs -ostomy | An incision that is closed again, against a permanent opening |
| hyper- vs hypo- | Above normal against below normal |
| -rrhagia vs -rrhoea | Bursting forth (bleeding) against a steady flow or discharge |
| brady- vs tachy- | Slow against fast |
| -osis vs -itis | An abnormal condition generally, against inflammation specifically |
| oligo- vs poly- | Too few or too little, against too many or too much |
Where decoding is not enough
The method works most of the time, not all of it. Some terms are eponyms named after a person — Parkinson’s disease, Crohn’s disease, the Glasgow Coma Scale — and carry no decodable parts at all. Others are historical and mean something narrower than the parts suggest: hypertension literally reads as high tension, but clinically it means one specific thing measured in one specific way.
Spelling conventions differ too. British texts keep the digraphs in haematology, anaemia and diarrhoea where American texts write hematology, anemia and diarrhea, and both appear in the literature. Where the two diverge the table lists both forms, and searching either will find the entry.