Understand the words
behind your health.

Medical terminology is the shared vocabulary of healthcare. It exists because ordinary language is not precise enough to describe a body: "tummy ache" could mean a dozen different things, while "epigastric pain" names one region and rules out the rest. Most of that vocabulary was assembled from Greek and Latin roots, which is why so much of it looks unfamiliar on a first reading and why almost all of it becomes predictable on a second.

The important thing about medical words is that they are built rather than invented. A long term is usually three or four short pieces joined together, and once those pieces are recognizable the word explains itself. That is what separates learning medical terminology from memorizing a list: a few dozen roots unlock several thousand words.

How is a medical word put together?

Three parts do the work. A prefix sits at the front and usually says where, when, how many or how much. A root carries the core meaning, almost always a body part or a substance. A suffix closes the word and says what is happening: a condition, a procedure, a measurement or a specialty.

Take pericarditis. Peri- means around, cardi- means heart, and -itis means inflammation, so the word describes inflammation of the tissue around the heart. The same suffix behaves identically everywhere: appendicitis, tonsillitis, dermatitis. Change the ending to -ectomy and the word becomes an operation to remove something instead.

Three endings are worth separating carefully, because one syllable changes the operation entirely. A name ending -ectomy means something was removed, -otomy means it was cut into, and -ostomy means a lasting opening was created. A gastrectomy, a gastrotomy and a gastrostomy are three different procedures on one organ.

Why do medical abbreviations cause so much trouble?

Clinical notes compress heavily, and the same few letters often carry different meanings in different settings. CVP is a chemotherapy combination on an oncology ward and central venous pressure in intensive care. PCP means primary care provider in a clinic and something else again in microbiology. An abbreviation is only safe alongside the context it was written in, which is why this dictionary expands them rather than listing them.

How does this medical dictionary work?

Every entry opens with a one-paragraph definition written in plain language, followed by a fuller explanation covering how something works, how it differs from the terms it is confused with, and what people most often get wrong about it. Where a genuine Greek or Latin origin exists it is given, because knowing the root makes the next word easier. Entries are cross-linked, so a term reached from a search leads on to the concepts that give it meaning.

The collection can be searched directly, browsed A to Z, or explored by topic and by medical specialty. Terms can be saved for later, and any entry can be read aloud. Definitions here explain what medical words mean; they cannot say what a result means for a particular person, and they are not a substitute for advice from a qualified professional.

Which pairs of terms are most often confused?

A handful of distinctions cause most of the misunderstanding, and none of them is difficult once stated plainly. A sign is something an examiner can observe or measure, while a symptom is something only the person feels: a fever is a sign, pain is a symptom. Acute and chronic describe how long something has lasted, not how serious it is, so a chronic condition is not necessarily mild and an acute one is not necessarily dangerous.

Benign and malignant describe how a growth behaves rather than how large it is. Idiopathic means the cause is unknown, not that no cause exists. Prognosis is the expected course of a condition, while diagnosis is the identification of it. And a risk factor is a statement about probability across a population, not a prediction about one person, which is why having one does not mean a condition will follow.