👉 In mathematics, an infinitesimal is a quantity that can be considered as small compared to any other quantity. It is defined as being less than one part in a million (1/10^6). For example, pi is an infinitesimal because it is smaller than 1/10^6 (e.g., π ≈ 3.14), and the square root of two is also an infinitesimal because it is smaller than 1/10^5 (e