"You hope he knows."
Translation:Vi esperas, ke li scias.
"You hope he knows," is somehow converted to "You hope that he knows" in the translation.
Caught me off guard. If I translate to spanish I can see where the "ke" comes from, but is there a way to understand this better?
The sentence after "ke" is a subclause and it's always expressed explicitly. There is a difference between two independent clauses "Vi esperas, li scias" (You hope, he knows) and "Vi esperas, ke li scias" (You hope that he knows). In the second one what you hope is put after "ke".