Usages of dubius
Cum responsum dubium est, magistra rogat ut discipula sinceram sententiam aperte dicat.
When the answer is uncertain, the teacher asks the student to state her honest opinion openly.
Quamquam vir crudelis videbatur, filia dixit eum non semper crudelem esse, sed interdum dubium et timidum.
Although the man seemed cruel, the daughter said that he was not always cruel, but sometimes uncertain and fearful.
Elon.io is an online learning platform
We have an entire course teaching Latin grammar and vocabulary.