Why medical terms can be decoded
Read this chart note: "History of cholecystitis. Now reports gastralgia. Exam shows hepatomegaly." It looks like a foreign language. It is actually three short sentences built from about eight word parts. Medical terminology is made of word roots, prefixes and suffixes, most of them from Greek and Latin, and each part keeps its meaning wherever it appears. Learn the parts once and you can decode thousands of terms instead of memorizing each one.
By the end of this page you will read that note as: "Has had an inflamed gallbladder. Now has stomach pain. The liver is enlarged."
The word root: the core meaning
A word root is the part of a term that carries its core meaning. In anatomy and physiology the root usually names a body part or a substance. In cardiology the root is cardi, "heart". In gastritis the root is gastr, "stomach".
A term can have more than one root. Gastroenterology has two: gastr (stomach) and enter (intestine). It means the study of the stomach and intestines.
| Root | Meaning | Example |
|---|---|---|
| cardi | heart | cardiology |
| gastr | stomach | gastritis |
| enter | intestine | gastroenterology |
| hepat | liver | hepatomegaly |
| nephr, ren | kidney | nephrectomy, renal |
| pulmon, pneum | lung | pulmonary, pneumonectomy |
| oste | bone | osteoma |
| my | muscle | myalgia |
| arthr | joint | arthroscopy |
| derm, cutane | skin | dermatology, subcutaneous |
| neur | nerve, the nervous system | neurology |
| hem, hemat | blood | hematology |
| cyt | cell | cytology |
| hist | tissue | histology |
| splen | spleen | splenomegaly |
| cyst | bladder, sac | cystitis |
| chole | gall, bile (the liver's digestive juice) | cholecystitis |
| ot | ear | otalgia |
| rhin | nose | rhinoplasty |
| hyster | uterus | hysterectomy |
| cost | rib | intercostal |
The combining form: root plus a linking vowel
Say "cardilogy" aloud. It is hard to say. Medical terms add a combining vowel, almost always o, to link parts smoothly: cardi + o + logy = cardiology. A root with its combining vowel is called a combining form, written with a slash: cardi/o, gastr/o, hepat/o.
Three rules decide whether the vowel stays:
- Between two roots, keep it, even if the second root starts with a vowel: gastr/o + enter/o + logy = gastroenterology.
- Before a suffix that starts with a consonant, keep it: hepat/o + megaly = hepatomegaly.
- Before a suffix that starts with a vowel, drop it: gastr/o + itis = gastritis, not "gastroitis".
Figure 1 shows both kinds of term taken apart.
The prefix: a modifier at the front
A prefix (pre- = before) is a word part placed before a root that changes its meaning. It often tells you where, how much, how many or how fast. Compare three breathing terms, all built on -pnea (breathing):
- tachypnea: fast breathing
- bradypnea: slow breathing
- apnea: no breathing
The suffix stayed the same. The prefix changed the meaning. Not every term has a prefix: cardiology and gastritis have none.
| Prefix | Meaning | Example |
|---|---|---|
| a-, an- | without, absent | apnea |
| brady- | slow | bradypnea |
| tachy- | fast | tachypnea |
| dys- | difficult, painful, abnormal | dyspnea (difficult breathing) |
| endo- | within | endoscopy |
| epi- | upon, over | epicranial (on top of the skull) |
| peri- | around | pericardium |
| sub- | under, below | subcutaneous |
| inter- | between | intercostal (between the ribs) |
| intra- | within, inside | intravenous (inside a vein) |
| hyper- | above, more than normal | hyperemia (more blood than normal in a part) |
| hypo- | below, less than normal | hypodermic (under the skin) |
| poly- | many, much | polycystic (with many sacs) |
| hemi-, semi- | half | hemisphere |
| bi- | two | bilateral (on both sides) |
| micro-, macro- | small, large | microscope |
Watch the pairs that look alike: inter- (between) and intra- (inside); hyper- (above normal) and hypo- (below normal). One letter changes the meaning completely.
The suffix: what kind of word it is
A suffix is a word part added at the end of a root. It usually tells you what kind of term you are reading: a condition, a procedure, a person, or a plain description. That is why you read it first.
| Kind | Suffix | Meaning | Example |
|---|---|---|---|
| Condition | -itis | inflamed (red, swollen, painful) | gastritis |
| Condition | -algia | pain | myalgia |
| Condition | -megaly | enlargement | hepatomegaly |
| Condition | -oma | a mass or swelling | osteoma, hematoma |
| Condition | -pathy | disease | neuropathy |
| Condition | -emia | a condition of the blood | hyperemia |
| Condition | -uria | a condition of the urine | dysuria |
| Procedure | -ectomy | cutting out, removal | appendectomy |
| Procedure | -tomy | cutting into | tracheotomy |
| Procedure | -ostomy | making a lasting opening | tracheostomy |
| Procedure | -scopy | looking inside with an instrument | arthroscopy |
| Procedure | -plasty | surgical repair or reshaping | rhinoplasty |
| Procedure | -gram | the recorded image or trace | angiogram |
| Field or person | -logy, -logist | study of, specialist in | cardiology, cardiologist |
| Description | -ac, -al, -ic, -ous | pertaining to | cardiac, renal, gastric, cutaneous |
| Thing | -cyte | cell | macrocyte (a large cell) |
Three surgical suffixes are easy to confuse. Here they are on the same root.
| -tomy | -ectomy | -ostomy | |
|---|---|---|---|
| Meaning | cutting into | cutting out | making an opening to the outside |
| Word roots | tom = cut | ec- = out, tom = cut | stom = mouth, opening |
| On the kidney | nephrotomy: an incision into the kidney | nephrectomy: removal of the kidney | nephrostomy: a tube opening from the kidney through the skin |
| Is the organ still there? | yes | no (all or part is removed) | yes, with a new opening |
How to decode a term
Decode pericarditis step by step:
- Read the suffix first. -itis: inflamed. This is a condition.
- Read the prefix next. peri-: around.
- Read the root or roots last. card: heart.
- Combine, starting from the suffix: inflamed, around, the heart. Pericarditis is an inflamed pericardium, the sac around the heart.
The rule: suffix, then prefix, then root. Reading left to right gives "around heart inflamed", which is backwards English. Starting from the suffix gives the kind of word first and the details after.
Now the chart note from the top of the page. Chole/cyst/itis: suffix -itis (inflamed), roots chole (gall) and cyst (bladder), so an inflamed gallbladder. Gastr/algia: suffix -algia (pain), root gastr (stomach), so stomach pain. Hepat/o/megaly: suffix -megaly (enlargement), root hepat (liver), so an enlarged liver.
Two roots for one organ
Many organs have two roots, one Greek and one Latin. The kidney is nephr (Greek) and ren (Latin). The lung is pneum (Greek) and pulmon (Latin). The skin is derm (Greek) and cutane (Latin). As a rough pattern, the Latin root often forms plain descriptive words (renal, pulmonary, cutaneous), and the Greek root forms the names of diseases, procedures and fields (nephritis, pneumonectomy, dermatology). Learn both roots for each organ, and a new term using either one will still make sense.
Where decoding stops working
Word parts give you the literal meaning. The medical meaning is usually the same, but not always. Artery comes from a Greek word for an air duct: ancient anatomists found arteries empty after death and guessed they carried air. You know from the previous topic that arteries carry blood away from the heart. When a literal decoding seems odd, check the definition. Word parts get you close; the glossary finishes the job.