- left to one's choice; not required or mandatory: Formal dress is optional.
- leaving something to choice.
Origin of optional
SynonymsSee more synonyms for optional on Thesaurus.com
1. discretional, elective, voluntary.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- possible but not compulsory; left to personal choice
Word Origin and History for unoptional
Online Etymology Dictionary, © 2010 Douglas Harper