I think you're asking an interesting question, but the wrong way around. And I wonder if you don't have some deeper question you're actually getting at.

As far as I can think, there is not a singular word in Ancient Greek that corresponds to something like, "sentient individual being" in the way we can use 'person' in modern English. anthropos would be the equivalent for 'human', and it would do for most uses of 'person'.

But Language doesn't restrict what we can think in the way your question suggests. If an Ancient Greek philosopher wanted to explore the idea of non-human sentient beinghood, they would express it in some other way.

The reason English uses 'person' in this way is really the result of the history of philosophy in Europe, and especially Anglophone circles, resulting in this concept of 'personhood'. No wonder Ancient Greek doesn't exactly correspond.

I said at the start that I think you're asking it the wrong way around. The 'right' way to ask these kinds of questions is to ask, "What do certain Ancient Greek words mean?" and use that as a tool in understanding AG philosophical ideas in context. Not to start with English language concepts and try to map them onto AG.