optional Definition

nonmandatory, elective, facultative, ex gratia, nonobligatory, mandatory, selectable, compulsory, extra, option, additional, opt, alternate, choice, voluntary, options, electives, alternative, intercom, arbitrary, discretionary, selective, conditional, protocol, permissive, cas, unofficial, slice, moratorium, covenant, add-on, opt-in, self-imposed, tell-tale, practitioner, obligatory, detachable, attachable, removable, adjustable, automatic, lockable, keyless, interchangeable, superfluous, variable, complimentary, preset, inbuilt, stowable, compatible, customizable, retractable, waterproof, enhanced, mountable, antilock, standard, expandable, threadless, gusseted, cocurricular, fillable, available, immersible, integrated, zoot, sealable, adaptive, subminiature, customised, insertable, octal, assignable, unlimited, ductless, antistatic, alphanumeric, scart, outboard, handy, closable, programmable, rainproof, plus, underslung, inline, unmounted, foldable, elasticized, manual, ripstop, weatherproof, lite, chamfered, transmissive, spline, flanged, extendable, lavalier,