When you're reverential, you treat someone or something with a lot of respect. You might speak about your beloved kindergarten teacher in a reverential voice.
To talk about someone in a reverential way or treat a family heirloom with reverential care is to act out of a deep, almost solemn kind of respect. The adjective reverential comes close to implying worship — a devoutly religious person feels reverential toward God, for example. It's rooted in the Latin word reverentia, "awe or respect," from revereri, "to stand in awe of, fear, or be afraid of."