Words similar to optional

Example sentences for: optional

How can you use “optional” in a sentence? Here are some example sentences to help you improve your vocabulary:

Ultra-fine limestone has been demonstrated as an optional enhancement over typical limestone reagent feed.
Participation was optional and informed consent was obtained for all interactions.
The museum also boasts a natural history section, but, compared to the riches of the rest of the collection, this is entirely optional viewing.
Alternative Allowance Allocation for Units in Certain Utility Systems With Optional Baseline.
Optional: A gene tree based on the multiple alignment A and the query Q annotated with orthology bootstrap confidence values for the query Q .