There are a lot of characteristics that can go into making a humans human, both physical and non-physical. Here is a list of some of the characteristics that describe what it means to be human.
2. Upright posture
3. Hands in which we can bring our thumbs all the way across the hand to our ring and little fingers, not opposable thumbs since the great apes also have opposable thumbs.
4. Extraordinary brains
6. Ability to control fire
7. Blushing. Humans are the only species known to blush.
8. Long childhoods
9. The ability to question our existence
10. Emotions (Love, hate, the desire to become more empathetic)
11. Our ability to alter the world around us and create artificial things
A person need not, necessarily, have all of these traits all the time to be considered to be human. For example, a person may have robotic arms or other robotic body parts and still be human.