A parasite is a creature that depends on another living thing, or host, for survival.
Perhaps you and your family have hosted a dinner at which you invited guests to eat food you prepared for them. Although a parasite depends on its host for food, often this guest is not invited! In fact, parasites can harm their hosts.
After all, the parasite gets strength from its host, often making the host weaker in the process.
Some parasites make people sick. For example, the disease malaria is caused by a parasite that is spread by mosquitos. Some types of parasites, such as protozoa, are so tiny they can only be seen with a microscope! Others, such as helminths, can be seen with the human eye when they become adults.
Parasites such as lice live outside of the body, while parasites like tapeworms can live inside of the body.
While there are many different types of parasites, most are typically smaller than the hosts they depend on!