Caustic alkali is a term used to describe a type of alkali that is highly corrosive and can cause severe burns. The most common caustic alkali is LYE, which is a three-letter word commonly used in soap-making and other chemical processes. It is also known as sodium hydroxide or potassium hydroxide and is a strong base that can dissolve organic materials. Caustic alkalis are used in many industries, including food processing, paper production, and metalworking.