👉 Reinhardt, a German mathematician, is often referred to as the first person who introduced the concept of "irreducible" in mathematics. In his famous 1852 paper, "Über die Darstellbarkeit einer Theorie durch eine Algebraische Transformation," he defined an algebraic transformation as one that "does not change any of the elements of a field." This definition led to the development of algebraic number theory and has been used in many branches of mathematics.