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optional ['ɔpʃ(ə)nəl] adj.
comp., MS	neobligāts (Pertaining to a component, parameter and so on that is not required or automatic)
English thesaurus
optional ['ɔpʃ(ə)nəl] abbr.
abbr.	opsh
abbr., polym.	opt.
Optional ['ɔpʃ(ə)nəl] abbr.
abbr., insur.	o/p
mil., abbr.	O

optional: 20 phrases in 5 subjects

Agriculture	1
General	4
Health care	2
Human rights activism	10
Microsoft	3