A human corpse is still a human, but it is not a person. One might say a dead person, but what we mean by that is that they have ceased to be a person. After all, how can a person be a person without life? If there hypothetical aliens, could they be persons? Sure. The Godhead consists of three persons; Father, Son, and Holy Spirit.
I think the best way to describe what a person is is something that has reason and consciousness. Consciousness is hard to define, but a major part of it is self-awareness and being able to distinguish between the “imagined” and the “actual.”
A human is simply genetic. I am a human because I am a homo sapient. It is in my DNA. My personhood may somehow be linked, but they are clearly not the same thing.
My best answer.