In computer science, cl usually refers to the abbreviation of Common Lisp. In some programming cultures, adding the prefix "cl" means that this is the name of a higher-level programming language or library. For example, pcl is the abbreviation of Parallel Common Lisp, which means that it is a general Lisp variant that supports parallel computing.

In chemistry, cl stands for chlorine or chloride. Therefore, if "cl" is added in front of the chemical substance, it means that it is a substance containing chlorine compounds. For example, ClO2 represents chlorine dioxide, Cl2 represents diatomic chlorine molecules, and Cl- is monoanionic chlorine.

In business, CL usually refers to the abbreviation of customer loyalty. If a company puts "cl" in their marketing slogan or advertisement, it means that the company is committed to providing a good customer experience and improving customer loyalty. For example, "our company focuses on providing high-quality services and products to enhance customer loyalty and trust."