Generic

Generic, in trademark law, refers to the status of a word or symbol commonly used to describe an entire type of product or service rather than to distinguish one product or service from another. An example is "raisin bran," used by several manufacturers of breakfast cereals to describe their products. Generic terms can never receive trademark protection because they do not serve the basic function of trademarks to distinguish goods and services in the marketplace, rather individuals use generic terms to refer to a type of product. 

While someone may have a trademark for a product, they can lose the trademark through genericide, where a term becomes generic to the common individual. For example, escalator was a trademarked term by its creator, but quite rapidly, the term became used to describe the moving stairs made by any company, not just the trademark owner.