Parasites live in a host from which they obtain food and protection. They may harm but usually do not benefit the host. The word "parasite" is derived from the Latin and Greek languages meaning, in general, "one who eats at the table of another." It is said that a "good" parasite does not overtly harm or kill its host. It is theoretically possible that a more benign parasite (e.g. Gasterophilus spp.) is much "older in eons of time" and it and its host have adjusted better to each other than a conceivably "newer" parasite (e.g. Strongylus spp.) which may be more harmful to its host.