Glossary

Why the vocabulary is worth having

Most of the frustration people report about a dermatology appointment is not that they were told too little. It is that the words went past too fast. A term you have met before does not stop you mid-sentence, and the difference between following an explanation and reconstructing it afterwards is often two or three words.

A term is also a key. It opens the published material, the patient organisations and the guidance maintained by health bodies. Without one you are left describing your skin repeatedly to people who then have to guess. This is why every page on this site names what it is describing, and why the spelling matters: dermatological vocabulary is largely Greek and Latin, and a term half remembered will not find anything useful in a search box.

How this vocabulary is built

Clinical language is far more systematic than it first sounds, and a handful of patterns account for a surprising share of it.

Endings carry the grammar. Anything ending in -itis denotes inflammation, so dermatitis is inflammation of the skin and blepharitis is inflammation of the eyelid margins. An ending in -osis denotes a condition or a process without implying inflammation at all. One in -oma denotes a growth, which is why melanoma sits in the same family as words describing things that are entirely harmless.

Beginnings carry the subject. Derm- and dermato- refer to skin, melano- to pigment, kerato- to the protein filling the outer layer, sebo- to the oil produced alongside hair. Combine a beginning with an ending and most of the word explains itself before anybody has defined it for you.

Qualifiers carry the caution, and they are the part most often skipped in reading. Words such as atypical, suspected, probable and consistent with are doing real work in a letter. Anything qualified that way is a description of an appearance rather than a conclusion about what something is, and reading past the qualifier turns a careful sentence into an alarming one.

None of this makes anybody fluent, and fluency is not the aim. Recognising the shape of a word is enough to stop it interrupting the sentence it sits in, which is the whole practical benefit. The rest can be looked up afterwards, without a clock running.

How these entries are written

Each term keeps to a couple of sentences, defines exactly one thing, and avoids defining it with three other terms you would then have to look up in turn. Where a definition genuinely depends on another idea, it links to that term rather than assuming it.

Nothing here describes what a condition does to a person, how it progresses, or what should be done about it. Those questions belong to the clinician who has examined the skin in question. A glossary that quietly answered them would be a diagnostic tool wearing a reference book as a disguise, and this one is not that.

Every entry is also cited from at least two pages elsewhere on the site. That constraint is deliberate: it stops the collection filling with words nobody meets in practice, and it means anything defined here is something a reader has a genuine chance of encountering in a letter or a consultation.

All of it is also published as an open dataset, in JSON and CSV under a licence that permits reuse of any kind provided the source is credited. The definitions are original prose, which is what makes giving them away ours to decide.

How to use this glossary

Look up a definition rather than an outlook. A glossary answers the question you actually have, which is what a word means. Searching instead for what a condition does to people produces a range of outcomes that may have nothing to do with your case, and it is the most reliable way to turn a term into an evening of unnecessary worry.

Each entry keeps to a couple of sentences on purpose, so that it can be quoted whole and read in the time you have. Where a term belongs to a particular depth in the skin, the entry carries the same cross-section that appears on every condition page, with that layer picked out.