Unified Medical Language System® (UMLS®) Basics

Lexical Entries

There is one lexical entry for each spelling or set of spelling variants in a particular part of speech. Each lexical record contains information on:

• Base form of the term
• The part of speech
• A unique identifier
• Rules for spelling variants

The base form of a term is the uninflected form of the item; the singular form in the case of a noun, the infinitive form in the case of a verb, and the positive form in the case of an adjective or adverb.

The lexicon recognizes eleven parts of speech:

Approximately eighty-six percent of the entries are nouns.