optional
UK: ˈɒp.ʃən.əl | US: ˈɑːp.ʃən.əl
adj. available to be chosen but not required
adj. left to one's choice; not compulsory
The word "optional" derives from the Latin optio (choice), combined with the suffix -al (pertaining to). The root "option" entered English via Old French option, retaining its core meaning of "a thing that may be chosen." The suffix -al (from Latin -alis) transforms nouns into adjectives, giving "optional" its modern sense of "subject to choice." This logical progression reflects how Latin roots were adapted into English to describe flexibility or non-mandatory conditions.
Wearing a tie is optional for the event.
The course includes optional modules for advanced learners.
She added all the optional features to her new car.
Participation in the survey is completely optional.
The software update comes with optional security enhancements.