If you've invited people over, offered to entertain, or let someone crash on your couch, then you're a host. Throw a fabulous party and you’ll be everyone’s favorite host. Do it when you're also hosting pneumonia germs, and your guests won't be so grateful.
The noun host refers to a person who receives and entertains guests. But hosting also has an ickier side: In biology, a host is an animal, plant or person that provides a home for another organism — like a parasite. Host also functions as a noun, meaning a multitude, horde, or great number. As in, "You will pick up a host of funky germs from drinking the water in rural India."