noun
contextually required token
Technical term in computing, especially in parsing or natural language processing, referring to a token that must appear in a given context.
この構文解析器では、文脈上の必す字句が欠けるとエラーになる。
In this parser, an error occurs if a contextually required token is missing.
Compound of 文脈上 (contextual) + の + 必す (required) + 字句 (token, phrase). The exact derivation is uncertain; it is a technical term likely coined in computing contexts.