Virus vs. Bacteria
The words virus and bacteria are often confused because they are both microscopic particles that can cause illness (many human ailments are either viral or bacterial infections). However, the two are quite different in form and function.
A virus is a microscopic particle that can cause and spread infectious disease in people, animals, and plants. There is some debate as to whether a virus is a living organism or just a structure that interacts with living organisms. Viruses have DNA or RNA enclosed in a protein coat, but lack many cellular structures. In general, there is no virus that is considered beneficial to living things.
Bacteria are any of a group of single-celled microorganisms that do not have a nucleus. Although bacteria can cause disease in living things, it also has many advantages. It helps with decomposition, makes soil fertile, and is used in food preparation and antibiotics. Harmful bacteria can be treated with antibiotics.
Viruses, the simplest life forms known to man (if they are to be considered life forms at all), are much smaller than bacteria. They must have a living organism or host on which to live and multiply, while bacteria can do so on non-living surfaces. Bacteria live in between cells while viruses live inside cells.