What is Sentient

Mankind had suffered through this very thought for ages; now and then, a scholar has raised the same question and approached it from a very different angle. Who am I? What is my purpose? Post AGI, this very question took on another meaning. If we are all but one, then the premise of Who am I loses its relevance. This very thought always had a baseline to compare with - with oneself, with fellow humans, with living things, with the feeling of emotions, the pain, the suffering, but now what is it really? What is Sentient?