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Extras are things which are not necessary in a situation, activity, or object, but which make it more comfortable, useful, or enjoyable.
Optional extras including cooking tuition.
Video: pronunciation of 'additive'
additive 的词库—— 柯林斯 英语词库
An additive is a substance which is added in small amounts to foods or other things in order to improve them or to make them last longer.