Chemical free or chemical-free is a term used in marketing to imply that a product is safe, healthy or environmentally friendly because it only contains natural ingredients. From a chemist's perspective, the term is a misnomer, as no matter that exists in Earth's ecosystems is free of chemicals. The term "chemical," by this definition, is roughly a synonym for matter, and common natural substances such as water and air are considered chemicals. This use of the term chemical in advertising to indicate that a product is free of synthetic chemicals, and the tolerance of its use in this fashion by the United Kingdom's Advertising Standards Authority, have been the subject of criticism.
A study of understandings of the term "chemical" among American undergraduates by chemist Gayle Nicoll in 1997 noted that "People may hold both a scientific and layman's definition of a chemical without linking the two together in any way. They may or may not consciously distinguish that the term 'chemical' has different connotations depending on the situation." The popular use of "chemical free" to indicate that something is free of purified or prepared chemicals is supported by the Oxford English Dictionary, which gives the following definition of "chemical": "A distinct substance or compound, esp. one which has been chemically prepared or purified."