Appendix A · Medical Word Roots, Prefixes, and Suffixes

Medical vocabulary looks like an enormous memorization problem and is not. It is a small construction kit — perhaps 400 pieces — used over and over. Learn the pieces and you stop memorizing terms altogether: you read them, the way you read a sentence in a language you speak.

This appendix has two halves. The first teaches the skill of taking an unfamiliar term apart. The second is the parts bin: prefixes, roots organized by body system, and suffixes, each with at least one real term you will actually meet. Read the first half once, properly. Then keep the tables open and stop looking words up.

A.1 How to Decode a Term You Have Never Seen

Almost every medical term is built from three kinds of part.

• The root (or combining form) carries the core meaning. It is almost always an organ, a tissue, a substance, or a process. Cardi- is heart. Nephr- is kidney. Hepat- is liver.
• The prefix modifies the root, and it does so in a small number of predictable ways: number, position, direction, negation, time, speed, size, or color. Peri- is around. Hyper- is above or excessive. A- is without.
• The suffix tells you what kind of thing the word names — a condition, a procedure, a specialty, or simply an adjective. -itis is inflammation. -ectomy is surgical removal. -ology is the study of.

A term needs a root. It may or may not have a prefix. It nearly always has a suffix.

The combining vowel

Roots are conventionally written with a slash and a vowel: cardi/o, nephr/o, gastr/o. That vowel — usually o, occasionally i — is a joint, and it follows one rule:

Keep the combining vowel when the next part begins with a consonant. Drop it when the next part begins with a vowel.

So cardi/o + -logy keeps the vowel, because l is a consonant: cardiology. But cardi/o + -itis drops it, because i is a vowel: carditis. The vowel is kept between two roots regardless — gastr/o + enter/o + -logy gives gastroenterology, vowel retained even though e is a vowel, because a word built of stacked roots would be unreadable otherwise. That single exception is worth knowing; it is why the long words have so many o's.

The vowel is not decoration. It exists because these words have to be said, and Greek and Latin do not tolerate the consonant clusters that direct joining would produce. "Cardlogy" is not pronounceable. "Cardiology" is.

Read the word backwards, then forwards

The efficient order is:

1. Suffix first. It tells you what category of thing you are looking at. If the word ends in -ectomy, you already know somebody took something out, and the rest of the word only has to tell you what.
2. Beginning next. The prefix, if there is one, sets position, number, or degree.
3. Middle last. The root or roots, read left to right, in order.

Try it on subhepatic. Suffix -ic, an adjective — so this word describes something. Prefix sub-, beneath. Root hepat, liver. Beneath the liver. A subhepatic abscess is a pocket of pus sitting under the liver, and you knew that before anyone told you.

Why there are two words for everything

Medical English draws on both Greek and Latin, and it uses them for different jobs. Latin roots tend to name plain anatomy; Greek roots tend to build the words for disease and procedure. That is why the kidney is renal in an anatomy lab and nephrectomy in an operating theatre. It is not inconsistency — it is two layers of borrowing, deposited centuries apart.

                    THE ANATOMY OF A MEDICAL TERM
        example:   e l e c t r o e n c e p h a l o g r a p h y

   ┌─────────────┬───────┬──────────────┬───────┬──────────────────────┐
   │  electr/o   │   +   │  encephal/o  │   +   │      -graphy         │
   ├─────────────┼───────┼──────────────┼───────┼──────────────────────┤
   │   ROOT 1    │combin-│    ROOT 2    │combin-│       SUFFIX         │
   │ "electrical"│ ing   │   "brain"    │ ing   │ "process of          │
   │             │ vowel │              │ vowel │  recording"          │
   └──────┬──────┴───┬───┴───────┬──────┴───┬───┴──────────┬───────────┘
          │          │           │          │              │
          │        kept          │        kept             │
          │     (root→root)      │   (next part begins     │
          │                      │    with consonant g)    │
          ▼                      ▼                         ▼
     WHAT is being          WHERE / WHAT           WHAT IS BEING DONE
     measured               structure              (read this FIRST)

   ═══════════════════════════════════════════════════════════════════
   READING ORDER:  ③ ─────────► ②  ◄───────────────────────── ①
                 middle       beginning                    suffix

   ASSEMBLED MEANING:  "the process of recording the electrical
                        activity of the brain"

   ─── contrast the same roots with a different suffix ───
     -graph   = the INSTRUMENT   → electroencephalograph  (the machine)
     -graphy  = the PROCEDURE    → electroencephalography (the test)
     -gram    = the RECORD       → electroencephalogram   (the tracing)

Seven worked examples, in increasing difficulty

1 · pericarditis peri- (around) + cardi (heart) + -itis (inflammation) = inflammation of the tissue around the heart. That tissue is the pericardium, the fibroserous sac described in §1.7. The decode also predicts the clinical picture: an inflamed serous membrane rubs, so you hear a friction rub; an inflamed sac may weep fluid, so the cavity can fill and compress the heart (Chapter 18).

2 · gastroesophageal gastr/o (stomach) + esophag (esophagus) + -eal (pertaining to). Pertaining to the stomach and the esophagus — specifically to the junction between them. Note the order: the roots are listed in the direction of the process being described. In gastroesophageal reflux, contents travel from stomach to esophagus, and the word says so.

3 · hepatosplenomegaly hepat/o (liver) + splen/o (spleen) + -megaly (enlargement) = enlargement of the liver and spleen together. Three parts, no prefix. The reason the two organs are named in one word is physiological: they share the portal venous circulation, so a condition that raises portal pressure enlarges both (Chapter 23).

4 · electroencephalography Taken apart in Figure A.1: the process of recording the brain's electrical activity. Contrast electrocardiography — same first root, same suffix, different organ.

5 · hypercholesterolemia hyper- (above normal, excessive) + chol/e (bile) + ster (solid, from stereos) + -ol (an alcohol, in the chemical sense) + -emia (blood condition) = an excess of cholesterol in the blood. Five pieces. Notice that the middle of the word is itself a chemical name that was built the same way: cholesterol was named because it was first isolated, as a solid alcohol, from gallstones (Chapter 24).

6 · esophagogastroduodenoscopy esophag/o + gastr/o + duoden/o + -scopy (process of visual examination). Looking at the esophagus, then the stomach, then the duodenum — in exactly the order the scope travels. The word is a map of the procedure. Everyone calls it an EGD, but only because the full form is long, not because it is unclear.

7 · thrombocytopenia thromb/o (clot) + cyt/o (cell) + -penia (deficiency) = a deficiency of the cells that form clots, i.e. of platelets. Follow the decode to the consequence and you have the whole clinical syndrome: too few clotting cells means bleeding, and bleeding into skin gives the pinpoint hemorrhages called petechiae (Chapter 17).

Traps

Roots that look alike and are not. These pairs generate the majority of student errors, and several of them generate real clinical errors too.

Plurals. Medical English keeps its Greek and Latin plurals, and the rules are regular.

Two of these carry information you will use: meninx is singular, so the three-layered covering of the brain is properly the meninges (Chapter 12); and phalanx is singular, so a single finger bone is a phalanx and the set is phalanges (Chapter 7).

A.2 Prefixes

A prefix never carries the core meaning of a term. It adjusts it — in number, position, negation, color, size, or time. That is the whole job, and it is why prefixes are worth learning first: there are few of them and they recur endlessly.

Prefixes of number and measurement

Prefixes of position and direction

Prefixes of negation

Prefixes and roots of color

Prefixes of size, degree, and comparison

Prefixes of time and speed

A.3 Roots by Body System

Roots are given in combining form. Where two roots mean the same thing, both are listed — the Greek and Latin doublets of §A.1 are the usual reason.

General and whole-body roots

Integumentary system

Skeletal system

Muscular system

Nervous system

Endocrine system

Cardiovascular system

Lymphatic and immune systems

Respiratory system

Digestive system

Urinary system

Reproductive systems

A.4 Suffixes

The suffix is the most informative single piece of a medical term, because it tells you what category of statement the word is making before you know anything about the anatomy. Learn these first if you learn nothing else.

Suffixes of condition and disease

The -itis / -osis distinction. -itis asserts inflammation, which means immune cells and the vascular response are present. -osis asserts only an abnormal condition, usually degenerative or accumulative, with no claim about inflammation. This is why tendinosis and tendinitis are different diagnoses of the same tendon, and why calling a degenerative problem an "-itis" leads to treating it with anti-inflammatories that cannot help (Chapter 10).

Suffixes of procedure and surgery

The -otomy / -ostomy / -ectomy family. These three differ in what happens after the knife. A tracheotomy is the act of cutting into the trachea. A tracheostomy leaves behind a permanent opening to the outside. A tracheectomy would remove it. One letter and one syllable separate an incision, a stoma, and an amputation.

Suffixes of specialty and practitioner

Suffixes of structure and adjective form

A.5 Fifteen Terms to Decode

Split each into its parts, write the literal meaning, then say what it means clinically. Do all fifteen before opening the answers — the value is in committing to a guess and being corrected, not in reading the correct answer first.

1. myelopathy
2. oliguria
3. thrombocytopenia
4. polydipsia
5. dysphagia — and then dysphasia
6. hemiparesis
7. pyelonephritis
8. splenomegaly
9. hypernatremia
10. tachypnea
11. arthrodesis
12. leukocytosis
13. retroperitoneal
14. encephalomyelitis
15. cholecystojejunostomy

Use this appendix alongside Appendix C for directional and regional vocabulary, and the Glossary for full definitions of terms in context.