possible but not necessary; left to personal choice
optional Idiom, Proverb
optional origin|optional|origin
n. Stipulation in international commodities contract whereby the seller may ship from either his foreign or his domestic resources. Be sure to enter that in the books as an optional origin order.
An optional idiom dictionary is a great resource for writers, students, and anyone looking to expand their vocabulary. It contains a list of words with similar meanings with optional, allowing users to choose the best word for their specific context.
Dictionary of similar words, Different wording, Synonyms, Idioms for Idiom, Proverb optional