Autoignition, also referred to as spontaneous ignition, refers to the process where a substance ignites without any external ignition source. There are different synonyms for autoignition, including self-ignition, auto-ignition, self-combustion, self-heat, and self-flammability. These terms are generally used interchangeably, and they all describe the same phenomenon. Autoignition can occur when a substance reaches its ignition temperature without any external heat source, resulting in a chemical reaction that releases heat. This process can occur in various substances, including fuels, chemicals, and organic materials. Understanding the synonyms and other associated terms can help in describing the phenomenon of autoignition in a more comprehensive way.