അർത്ഥം : Morally or legally constraining or binding.
ഉദാഹരണം :
Attendance is obligatory.
An obligatory contribution.
Possible but not necessary. Left to personal choice.
optionalഅർത്ഥം : Required by obligation or compulsion or convention.
ഉദാഹരണം :
He made all the obligatory apologies.