Medical Terminology Essentials: 300 Terms and Word Parts

Decode clinical vocabulary through 300 essential terms and word parts.

300 cardsLast updated 2026-08-16

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Medical terminology becomes manageable the moment you learn how the words are built. This 300-card foundation combines high-yield prefixes, suffixes and combining forms with the common directional, diagnostic, procedural and body-system terms built out of them. Each card explains the term in plain English and, where it helps, breaks it into components — so the pattern transfers to a term you have never seen instead of stopping at the ones you memorized. Import it and the whole deck joins your spaced-repetition schedule. Terms you already know stretch out and drop out of sight; the ones that keep slipping come back until they stop slipping. What goes down is the number of terms you still don't know — not the time it takes to flip past 300 cards you mostly do.

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Showing 100 representative cards from the full 300-card deck.

Front	Back
a-	Prefix meaning without or not. It is attached directly to the base: atypical means not typical. Medical terms may use an- before a vowel sound, as in anuria.
brady-	Prefix meaning slow. Breaks down as brady- = slow. Example: bradycardia means a slow heart rate.
tachy-	Prefix meaning fast or rapid. Breaks down as tachy- = rapid. Example: tachypnea means rapid breathing.
inter-	Prefix meaning between or among. Breaks down as inter- = between. Example: intercostal means between the ribs.
sub-	Prefix meaning under or below. Breaks down as sub- = below. Example: subcutaneous means beneath the skin.
trans-	Prefix meaning across, through, or beyond. Breaks down as trans- = across. Example: transdermal means through the skin.
bi-	Prefix meaning two or twice. Breaks down as bi- = two. Example: bilateral means affecting both sides.
poly-	Prefix meaning many or much. Breaks down as poly- = many. Example: polyuria means excessive urination.
micro-	Prefix meaning small. Breaks down as micro- = small. Example: microcyte means a small red blood cell.
hemi-	Prefix meaning half. Breaks down as hemi- = half. Example: hemiplegia means paralysis of one side of the body.
dys-	Prefix meaning bad, difficult, or painful. Breaks down as dys- = difficult or abnormal. Example: dysphagia means difficult swallowing.
-emia	Suffix meaning blood condition. Breaks down as -emia = blood condition. Example: bacteremia means the presence of bacteria in the blood.
-tomy	Suffix meaning cut into or incision. Breakdown: -tomy = incision. Example: tracheotomy is an incision into the trachea.
-plasty	Suffix meaning surgical repair or reshaping. Breaks down as -plasty = repair. Example: rhinoplasty means surgical repair of the nose.
-graph	Suffix meaning instrument used to record or write. Breaks down as -graph = recorder. Example: a cardiograph records heart activity.
-stomy	Suffix meaning creating an opening. Breaks down as -stomy = opening. Example: colostomy means surgically creating an opening into the colon.
-rrhagia	Suffix meaning excessive flow or bursting forth. Breaks down as -rrhagia = excessive bleeding or discharge. Example: menorrhagia means heavy menstrual bleeding.
-meter	Suffix meaning instrument for measuring. Breaks down as -meter = measuring device. Example: a thermometer is an instrument for measuring temperature.
-logy	Suffix meaning study of. Breaks down as -logy = study. Example: cardiology is the study of the heart.
-malacia	Suffix meaning abnormal softening. Breaks down as -malacia = softening. Example: osteomalacia means softening of bone.
cardi/o	Combining form meaning heart. Breaks down as cardi/o = heart. Example: cardiology focuses on heart function.
enter/o	Combining form meaning intestine, usually the small intestine. Breaks down as enter/o = intestine. Example: enteritis means inflammation of the intestine.
neur/o	Combining form meaning nerve. Breaks down as neur/o = nerve. Example: neurology is the study of the nervous system.
oste/o	Combining form meaning bone. Breaks down as oste/o = bone. Example: osteomalacia means abnormal softening of bone.
dermat/o	Combining form meaning skin. Breaks down as dermat/o = skin. Example: dermatology is the study of skin.
immun/o	Combining form meaning immunity or immune protection. Breaks down as immun/o = immunity. Example: immunology is the study of the immune system.
glyc/o	Combining form meaning sugar or glucose. Breaks down as glyc/o = sugar. Example: hypoglycemia means low blood sugar.
ot/o	Combining form meaning ear. Breaks down as ot/o = ear. Example: otitis means inflammation of the ear.
psych/o	Combining form meaning mind. Breaks down as psych/o = mind. Example: psychology studies behavior and mental processes.
erythr/o	Combining form meaning red. Breaks down as erythr/o = red. Example: erythrocyte means red blood cell.
steat/o	Combining form meaning fat or sebum. Breaks down as steat/o = fat. Example: steatorrhea means fat in the stool.
-a	Plural ending in some Greek- or Latin-derived medical nouns, especially singular forms ending in -um or -on: bacterium → bacteria; ganglion → ganglia. Do not assume every word ending in -a is plural.
-us	Latin singular ending often seen in anatomical terms. Breaks down as -us = singular form. Example: bronchus is singular; bronchi is plural.
-is	Greek/Latin singular ending in some medical terms. Breaks down as -is = singular form. Example: diagnosis is singular; diagnoses is plural.
-on	Greek singular ending seen in many medical terms. Breaks down as -on = singular form. Example: ganglion is a single nerve cluster; ganglia is plural.
-ices	Plural ending used for some words ending in -ix. Breaks down as -ices = plural form. Example: appendix becomes appendices.
posterior	Directional term meaning toward the back of the body. Contrast: posterior is opposite anterior. Example: the spine is posterior to the sternum.
inferior	Directional term meaning below or lower. Contrast: inferior is opposite superior. Example: the stomach is inferior to the lungs.
lateral	Directional term meaning away from the midline. Contrast: lateral is opposite medial. Example: the arms are lateral to the chest.
distal	Directional term meaning farther from the point of attachment or origin. Contrast: distal is opposite proximal. Example: the fingers are distal to the elbow.
deep	Directional term meaning farther from the surface. Contrast: deep is opposite superficial. Example: bone is deep to skin.
contralateral	Directional term meaning on the opposite side of the body. Breaks down as contra- = opposite, -lateral = side. Example: the right arm is contralateral to the left leg.
coron/o	Combining form meaning crown or encircling. In medicine it appears in coronary terms because the coronary vessels encircle the heart. Example: coronary arteries supply the heart muscle.
arteri-	Artery. Used in terms like arterial and arteriogram. It points to vessels carrying blood away from the heart; contrast with ven- for veins.
angi/o	Vessel, usually a blood vessel. Breakdown: angi- = vessel; -o- = combining vowel. Example: angioplasty is a procedure to open a narrowed vessel.
hem/o	Blood. Breakdown: hem- = blood; -o- = combining vowel. Example: hemoglobin is the oxygen-carrying protein in red blood cells.
-cardia	Heart rate or heart condition. Example: tachycardia means fast heart rate, while bradycardia means slow heart rate.
bronch/o	Bronchus, a main airway branch. Breakdown: bronch- = bronchus; -o- = combining vowel. Example: bronchitis means inflammation of the bronchial tubes.
laryng/o	Larynx, or voice box. Breakdown: laryng- = larynx; -o- = combining vowel. Example: laryngitis is inflammation of the larynx, which can cause hoarseness.
alveol/o	Alveolus, a tiny air sac in the lung. Breakdown: alveol- = air sac; -o- = combining vowel. Example: alveolar gas exchange happens in the small sacs at the end of the airways.
sinus/o	Sinus, an air-filled cavity. In respiratory terms it often refers to the paranasal sinuses. Example: sinusitis means inflammation of the sinus lining.
-oxia	Oxygen level or oxygen condition. Example: hypoxia means low oxygen; anoxia means no oxygen.
an/o	Anus. Breakdown: an- = anus; -o- = combining vowel. Example: anal fissure means a tear near the anus.
proct/o	Rectum and anus. Breakdown: proct- = anus/rectum; -o- = combining vowel. Example: proctitis means inflammation of the rectum.
ren/o	Kidney. Breakdown: ren- = kidney; -o- = combining vowel. Example: renal refers to something related to the kidney.
ureter/o	Ureter, the tube from kidney to bladder. Breakdown: ureter- = ureter; -o- = combining vowel. Example: ureteral stone means a stone lodged in the ureter.
-uria	Urine condition or urine presence. Example: hematuria means blood in the urine; dysuria means painful or difficult urination.
bucc/o	Cheek. Example: buccal mucosa is the lining of the inside of the cheek; buccal means relating to the cheek.
duoden/o	Duodenum, the first part of the small intestine. Breakdown: duoden- = duodenum; -o- = combining vowel. Example: duodenal ulcer means an ulcer in the duodenum.
mast/o	Breast. Breakdown: mast- = breast; -o- = combining vowel. Example: mastitis is inflammation of breast tissue.
hyster/o	Uterus. Breakdown: hyster- = uterus; -o- = combining vowel. Example: hysterectomy is surgical removal of the uterus.
oophor/o	Ovary. Breakdown: oophor- = ovary; -o- = combining vowel. Example: oophorectomy is removal of an ovary.
cervic/o	Neck or cervix. Breakdown: cervic- = neck/cervix; -o- = combining vowel. Example: cervical may refer to the neck or to the cervix, so context matters.
ovul/o	Egg cell or ovum. Breakdown: ovul- = egg; -o- = combining vowel. Example: ovulation is the release of an egg from the ovary.
endocrin/o	Endocrine glands; internal secretion. Example: endocrinology is the study of hormone-producing glands and their secretions.
adren/o	Adrenal gland. Breakdown: adren- = adrenal gland; -o- = combining vowel. Example: adrenal hormones help the body respond to stress.
calci/o	Calcium. Breakdown: calci- = calcium; -o- = combining vowel. Example: calcium balance is influenced by parathyroid hormone.
myel/o	Combining form meaning spinal cord or bone marrow, depending on context. In nervous-system terms it usually refers to the spinal cord. Example: myelopathy is disease of the spinal cord.
-paresis	Suffix meaning partial paralysis or weakness. It signals reduced movement, not complete loss. Example: hemiparesis is weakness on one side of the body.
chondr/o	Combining form meaning cartilage. It appears in terms about flexible connective tissue at joints and ribs. Example: chondritis is inflammation of cartilage.
-rrhaphy	Suffix meaning surgical suturing or stitching together. Example: herniorrhaphy is repair with sutures.
trich/o	Combining form meaning hair. It appears in hair-related disorders and procedures. Example: trichology is the study of hair and scalp conditions.
-sepsis	Suffix associated with infection or microbial contamination, as in antisepsis. Important distinction: sepsis is a life-threatening syndrome of organ dysfunction caused by a dysregulated response to infection, not simply any infection.
retin/o	Combining form meaning retina, the light-sensitive layer at the back of the eye. Example: retinopathy means disease of the retina.
-tropia	Suffix meaning turning or eye deviation. It is used for misalignment of the eyes. Example: esotropia means inward turning of an eye.
acous/o	Combining form meaning hearing or sound. It appears in terms about sound perception and hearing loss. Example: acoustic relates to sound.
-scope	Suffix or word part meaning instrument for viewing. It names tools used to look inside the body or examine structures. Example: otoscope is an instrument for viewing the ear.
crani/o	Combining form meaning skull. It is used in surgical and anatomical terms. Example: craniotomy is an opening into the skull.
fasci/o	Combining form meaning fascia, a fibrous connective tissue layer. Example: fasciitis is inflammation of fascia.
-oma	Suffix meaning tumor or mass. It can be benign or malignant depending on context, so the word part alone does not tell severity. Example: lipoma is a fatty mass.
mono-	Prefix meaning one or single. Example: monoparesis means weakness in one limb.
retro-	Prefix meaning backward or behind. Example: retrograde means moving backward or in reverse.
extra-	Prefix meaning outside or beyond. Example: extracranial means outside the skull.
interstitial	Pertaining to the spaces within a tissue or between tissue elements. Example: interstitial fluid occupies the spaces between cells.
erythema	Redness of the skin or mucous membranes, usually from increased blood flow. Example: erythema can appear around an irritated area.
glaucoma	A group of eye disorders that can damage the optic nerve, often linked to pressure changes. It is distinct from lens clouding. Example: glaucoma affects peripheral vision first in many cases.
-dipsia	A suffix meaning thirst. Breakdown: no further parts; often appears in symptom terms. Example: polydipsia means excessive thirst, contrasted with normal thirst after exercise.
-ion	A noun-forming suffix meaning process or condition. Breakdown: no further parts; often turns an action into a state. Example: abrasion is a rubbing-away injury, not a surgical procedure.
-genic	Suffix meaning producing, produced by, or caused by. Example: cardiogenic shock originates from inadequate cardiac pumping.
-phoresis	A suffix meaning carrying or transmission. Breakdown: no further parts; often refers to movement or transfer. Example: electrophoresis uses electricity to move molecules, unlike passive diffusion.
-therapy	A suffix meaning treatment. Breakdown: no further parts; refers to care intended to improve a condition. Example: chemotherapy is drug treatment, not a diagnostic test.
acro-	A prefix meaning extremity or topmost part. Breakdown: acro- = extremity. Example: acromegaly involves enlarged extremities, not the trunk.
counter-	A prefix meaning opposite, opposing, or in response to. Breakdown: counter- = against. Example: counterpressure is pressure applied in opposition to movement.
em-	A prefix meaning in or within; a variant of en- used before certain consonants. Example: emphysema contains em- as a form of en-, though many medical words beginning with em- are not cleanly divisible for teaching purposes.
mega-	A prefix meaning great or large. Breakdown: mega- = large. Example: megacolon is an abnormally large colon, not just a full colon.
ortho-	A prefix meaning straight, correct, or normal. Breakdown: ortho- = straight/correct. Example: orthodontics focuses on correcting tooth alignment.
pre-	A prefix meaning before. Breakdown: pre- = before. Example: prenatal means before birth, unlike postnatal.
ex-	A prefix meaning out of or away from. Breakdown: ex- = out. Example: excision means cutting out or removing tissue.
hematemesis	Vomiting blood. Breakdown: hemat- = blood, -emesis = vomiting. Example: hematemesis refers to blood in vomit, not coughing blood.
dyspnea	Difficult or labored breathing. Breakdown: dys- = difficult, -pnea = breathing. Example: dyspnea means shortness of breath, unlike a cough.

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Editorial method and sources

Memly's editors use the primary sources below to check scope and terminology, then independently write and review the cards.

MedlinePlus: Understanding Medical Words