optional
/ˈɑpʃənəɫ/
available to be chosen but not required
optional in a sentence
“The extra features are optional.”
Origin of optional
Latin optio choice (from optare to choose) + -al
Related Words
ancillary
providing necessary support; supplementary
predicate
to base something on; require as a precondition
entail
to involve something as a necessary consequence
stipulate
to specify as a condition or requirement
prerequisite
something required as a prior condition
contingent
dependent on something else; conditional