Medical Prefixes, Suffixes and Root Words Explained

Almost every medical term you will meet is built from three kinds of word part: a prefix at the front, a root in the middle and a suffix at the end. Learn the parts and the few rules for joining them, and you can read terms you have never seen. This guide groups the most common parts by meaning, which is easier to learn from than an alphabetical list, and works through examples from Encodr's free Medical Terminology course.

The parts of a medical term

• Prefix (P): starts the term and changes the root's meaning, usually by number, position, direction, time or negation. Example: brady- (slow).
• Word root (WR): the core meaning, usually a body part. Example: cardi (heart).
• Combining vowel (CV): usually o, sometimes i, used to join parts. Example: the o in cardi/o.
• Combining form (CF): the root plus its combining vowel, written with a slash. Example: cardi/o.
• Suffix (S): ends the term and usually names a procedure, condition or disease. Example: -logy (study of).

Three rules govern how they fit together:

1. A combining vowel stays before a suffix that starts with a consonant: hepat/o/megaly (enlargement of the liver).
2. It usually drops before a suffix that starts with a vowel: hepat/itis (inflammation of the liver).
3. Two roots joined together keep the vowel between them (gastr/o/enter/o/logy), and a prefix never takes one (intra/ven/ous).

To define a term, split it, define each part, then start with the suffix and read the rest from the left. Peri/card/itis: -itis (inflammation), peri- (around), card (heart), so inflammation of the tissue around the heart.

Prefixes, grouped by meaning

Prefixes are easy to mix up, because many come in near-identical pairs.

The pairs to learn together: inter- and intra-, hyper- and hypo-, para- and peri-, ab- and ad-, ante- and anti-, di- (two) and dia- (through), and brady- and tachy-. Those last two are everywhere in vital signs: tachycardia is a fast heart rate, bradypnea is slow breathing. You will hear them constantly in an EMS setting; EMT patient assessment step by step shows where.

Suffixes, grouped by job

Suffixes do most of the work in a term, and they fall into a few families.

Surgical suffixes

The trio that causes the most mistakes is -tomy, -ectomy and -stomy: cutting into, cutting out, and making an opening.

Diagnostic suffixes

Three pairs follow the same pattern, with one word for the tool and one for the process:

• -graph (instrument) and -graphy (process), plus -gram (the record itself). An electrocardiogram is the tracing.
• -scope (instrument) and -scopy (viewing). A bronchoscope is used to perform a bronchoscopy.
• -meter (instrument) and -metry (measuring). Audiometry measures hearing.

Condition and disease suffixes

• Inflammation: -itis.
• Condition: -ia, -ism, -osis (abnormal condition), -iasis.
• Disease and lack: -pathy (disease), -penia (deficiency), -emia (blood condition).
• Shape and size changes: -megaly (enlargement), -malacia (softening), -sclerosis (hardening), -stenosis (narrowing), -ectasis (widening).
• Flow: -rrhage (bleeding), -rrhea (discharge), -rrhexis (rupture).
• Growth: -plasia (formation), -trophy (development), -oma (tumor).
• Function: -algia and -dynia (pain), -plegia (paralysis), -paresis (slight paralysis), -phagia (swallowing), -pnea (breathing).

Pertaining-to suffixes

-ac, -al, -ar, -ary, -eal, -ic, -ior and -ous all mean "pertaining to." Cardiac, renal and venous are the same move on different roots.

Root words by body system

Roots are the largest group, and they are easiest to learn alongside the system they belong to. A starter set from unit 1 of the course:

• Organs: cardi/o heart, gastr/o stomach, hepat/o liver, nephr/o kidney, pneum/o lung, enter/o intestine, col/o colon, thorac/o chest.
• Nerves, bone and muscle: neur/o nerve, encephal/o brain, oste/o bone, arthr/o joint, chondr/o cartilage, my/o muscle.
• Blood and cells: hemat/o and hem/o blood, erythr/o red, leuk/o white, cyt/o cell, hist/o tissue, angi/o vessel, arteri/o artery, ven/o vein.

Each system unit then adds its own: derm/o and onych/o for skin and nails, nephr/o and ren/o for kidney, cyst/o for bladder, hyster/o for uterus. Several systems have two roots with the same meaning, one Greek and one Latin (nephr/o and ren/o, both kidney), and you need both.

Some parts are shared with lab science. The suffix -coccus means berry-shaped, which is why spherical bacteria are cocci, chains are streptococci and clusters are staphylococci. If you take microbiology, gram-positive vs gram-negative bacteria and what's in Microbiology use this vocabulary constantly.

Putting it together: worked examples

Notice that the same few parts keep coming back. That is the argument for learning parts in groups: each one you add multiplies the number of terms you can read. Chunking explains why experts read a term like cholecystectomy as two or three units rather than fifteen letters.

How to learn them

Group parts by meaning, as above, rather than alphabetically. Quiz in both directions: part to meaning, and meaning to term. Put the look-alike pairs on cards that ask for the difference. And mix the groups once you know them, instead of drilling prefixes for a week and then suffixes for a week; interleaving vs blocking explains why mixed practice holds up better on a test. How to memorize a list, a table or a formula sheet covers turning tables like the ones here into cards.

For the full study plan, see how to learn medical terminology fast, and for every unit in the course, what's in Medical Terminology. The course's first unit gives a card to each of the roughly 200 word-part groups in the OpenRN textbook. It is free in the Medical Terminology course on Encodr, alongside the other courses in the free gen ed flashcards list.