"Non-invasive" refers to a medical or testing procedure that doesn't require the penetration of the body or the use of instruments that break the skin or enter body cavities. In the context of a non-invasive prenatal paternity test, it means that the procedure doesn't involve any invasive methods such as taking a sample directly from the uterus or the amniotic sac. Instead, it relies on samples like a blood sample from the pregnant mother, making it safer and less intrusive than invasive methods.