noun
inherently optional token
Technical computing term for a token that is optional by its nature, not because of a grammar rule. Used in parsing and compiler contexts.
このパーサーでは、固有選択字句は常に省略可能とみなされる。
In this parser, inherently optional tokens are always considered omissible.
Compound of 固有 (inherent) + 選択 (selection/optional) + 字句 (token/character phrase). A technical term likely coined in Japanese computing contexts.