By-product is a term used to refer to something that is produced as a result of a particular process or activity. It is synonymous with terms such as residue, side effect, offshoot, spin-off, fallout, and second product. These terms refer to the secondary or unintended products that result from a particular process or activity. For example, the residue left behind in a chemical reaction, the side effects of a medication, or the spin-off of a project. Some synonyms include unintended consequences, auxiliary product, corollary, epiphenomenon, aftermath, and collateral effect. These synonyms convey the same idea as by-product and can be used interchangeably depending on the context of the conversation.