Many second Intergovernmental Negotiating Committee on Plastic Pollution (INC-2) delegates indicated that the scope of the treaty should include plastic alternatives and substitutes. However, there are no internationally agreed definitions of plastic alternatives nor plastic substitutes. Sound definitions will support fully informed treaty negotiations. International agreements emphasize the need to consider the human health, environmental, economic, and social risks, costs, and implications of alternative substances. International legal instruments also note that when considering substitutes, the potential environmental benefits or penalties of substitute materials or activities (i.e., negative externalities) must be considered. The United Nations Conference on Trade and Development (UNCTAD) has developed the following plastics alternatives and substitute definitions: Plastics Alternatives are plastics not made with conventional fossil-fuel-based polymers. In other words, plastic alternatives are bioplastics3. Despite UNCTAD’s descriptions below, bioplastics are not necessarily ‘better plastics’. Plastic substitutes are all other non-plastic materials that may be used to replace synthetic fossil fuel-based polymers and bioplastics. Some examples are glass, leather, wood, silk, paper, cotton, wool, stone, ceramic, and aluminum.