słownik rosyjsko - angielski
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факультативный (придмет, курс) po angielsku:
1. optional
The word "the" is optional in this sentence.
Although it was optional, everyone wore their formal clothes.
is english your optional subject or obligatory?
In some countries, tipping a waiter isn’t optional, it’s obligatory.
He thinks Phisical Education should be optional.
An air conditioner is available as an optional extra.