parasite

Parasite is a organism that feeds off their host and give the hosts nothing from it,and example of a parasite and the parasites host is a leech and a human with the leech being the parasite being rewarded gaining blood from this experience and the human losing from it losing blood,STAY AWAY FROM LEECHES and also stay safe.

oh look its a mosquito its going to suck up all your blood like the parasite it is