A Lewis acid is a substance that can accept a pair of electrons to form a chemical bond. Some common synonyms for Lewis acid include electrophile, acceptor, and electron acceptor. Another synonym is Lewis base-complex, which is a substance that binds to a Lewis acid. This complex is also known as an adduct or a donor-acceptor complex. Additionally, a Lewis acid can also be referred to as a cationic acid, as it is a positive-ion that can accept electrons. Other related terms can include Lewis acid catalysts, which are compounds that speed up reactions that involve Lewis acids. However, with all these different synonyms, the core concept of a Lewis acid remains the same: a substance that can accept an electron pair to form a new chemical bond.