Lepton

A lepton is an elementary particle of matter which does not undergo strong interactions, but is subject to the Pauli exclusion principle (apart from quarks and bosons, all known particles in the universe are leptons). The best known of all leptons is the electron which governs nearly all of chemistry as it is found in atoms and is directly tied to all chemical properties. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons), and neutral leptons (better known as neutrinos). Charged leptons can combine with other particles to form various composite particles such as atoms and positronium, while neutrinos rarely interact with anything, and are consequently rarely observed.