optional op‧tion‧al [ˈɒpʆnəl ǁ ˈɑːp-] adjective
if something is optional, you can choose whether or not you have it, do it, or use it:

• You can have a 17-inch monitor as an optional extra (= something that is additional to or better than the basic type ) .

• The use of a password to access the system is optional.

— compare standard2

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optional UK US /ˈɒpʃənəl/ adjective
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 — Cf. optional extra

Financial and business terms. 2012.