Valency

Valency (or valence) refers to the argument-taking potential of verbs, and sometimes also adjectives and nouns.

Example
the verb open is associated with the semantic roles Agent, Theme, and Instrument (e.g. John [AGENT] opened the door [THEME] with his key [INSTRUMENT]), while the verbs ran and arrive are only associated with the Agent role (Bill ran) or Theme role (John arrived), respectively.

Comments
This term has always been more widespread in European linguistics than in American linguistics.

Synonyms
The following terms mean roughly the same as valency:
 * argument structure
 * subcategorization frame
 * arity
 * adicity

Origin
The term was adopted from chemistry by Lucien Tesnière.

Other languages
German Valenz

Links
Utrecht Lexicon of Linguistics