Abstract
This paper considers the nature of lexical knowledge and its role in language and
information processing. The lexicon is the central component of language and plays
a pivotal role in current linguistic theory [3, 4] and, increasingly, in natural language
processing systems [5-7]. The lexicon embodies information aboutthe lexical items
ofthe language and serves as the foundation for morphologic, syntactic, and semantic
processing. The differences as well as commonalities among dictionaries, thesauri,
and lexicons are discussed, and distinctions between words, lexical items, and terms
are drawn. Next, the scope and content ofthe SPECIALIST lexicon are presented, followed
by a discussion of certain writing conventions that can be troublesome for text processing
applications. One approach to handling orthographic and other lexical variation is
discussed in a section that reports on the design and implementation of the SPECIALIST
lexical programs. The paper concludes with a discussion of controlled terminologies
for the medical domain. Throughout the discussion, examples are drawn from the SPECIALIST
lexicon and from the other UMLS knowledge sources [8,9].
Keywords
Lexical Knowledge - Natural Language Processing - Medical Terminologies