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English definition of “optional”

optional

adjective     /ˈɒpʃənəl/
COMMERCE something that is optional is something that you can buy or do if you want to, but that you do not have to buy or do: Optional plug-ins cost a further $50 on average. optional accessories/components
optional extra COMMERCE, MARKETING something that can be added, at extra cost, to a basic product or service to make it more attractive, efficient, etc.: Some car manufacturers offer advanced stereo systems as an optional extra on their more expensive models.
(Definition of optional adjective from the Cambridge Business English Dictionary © Cambridge University Press)
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