The Semantics of a Definiendum Constrains both the Lexical Semantics and the Lexicosyntactic Patterns in the Definiens

Most current definitional question answering systems apply one-size-fits-all lexicosyntactic patterns to identify definitions. By analyzing a large set of online definitions, this study shows that the semantic types of definienda constrain both lexical semantics and lexicosyntactic patterns of the definientia. For example, “heart” has the semantic type [Body Part, Organ, or Organ Component] and its definition (e.g., “heart locates between the lungs”) incorporates semantic-typedependent lexicosyntactic patterns (e.g., “TERM locates ...”) and terms (e.g., “lung” has the same semantic type [Body Part, Organ, or Organ Component]). In contrast, “AIDS” has a different semantic type [Disease or Syndrome]; its definition (e.g., “An infectious disease caused by human immunodeficiency virus”) consists of different lexicosyntactic patterns (e.g., “...causes by...”) and terms (e.g., “infectious disease” has the semantic type [Disease or Syndrome]). The semantic types are defined in the widely used biomedical knowledge resource, the Unified Medical Language System (UMLS).