Biodegradation: The process by which an organic material degrades through the action of microorganisms over a period of time. Biodegradation can occur in either aerobic (with oxygen) or anaerobic (without oxygen) environments. 

Degradation: The process by which a material is broken down into smaller pieces but never completely disappears. Plastic degradation can be initiated by the presence of oxygen, UV light, and heat. In many cases these products begin to degrade the moment they are manufactured, resulting in an abbreviated shelf-life.