👉 In the context of mathematics, "piazin" is a mathematical concept used in algebra and number theory. It refers to the set of all rational numbers that can be expressed as a ratio of two integers (a/b), where a and b are coprime positive integers. The term was introduced by G. H. Hardy in his book "A Mathematician's Apology" in 1940, where he defined it for the first time. It is also known as the