Infinitesimal

In mathematics, an infinitesimal, or infinitely small number, is a number that is greater in absolute value than zero yet smaller than any positive real number. A number x ≠ 0 is an infinitesimal iff every sum |x| + ... + |x| of finitely many terms is less than 1, no matter how large the finite number of terms. In that case, 1/x is larger than any positive real number. Infinitesimals, obviously, are not real numbers, so "operations" on them aren't familiar.

See also

• Hyperreal number
• Infinitesimal calculus
• Surreal number