| Term | Definition |
| competition | When 2 or more populations try to use the same resource |
| parasitism | a relationship between two species in which one species, the parasite, benefits from the other species, the host, which is harmed |
| symbiosis | a relationship in which two different organisms live in close association with each other |
| mutualism | a relationship between two species on which both species benefit |
| predator | an organism that eat all or part of another organism |
| prey | an organism that is killed and eaten by another organism |
| communalism | a relationship between two organisms in which one organism benefits and the other is unaffected. |