In arithmetic and number theory, the least common multiple, lowest common multiple, or smallest common multiple of two integers "a" and "b", usually denoted by lcm("a", "b"), is the smallest positive integer that is divisible by both "a" and "b". Since division of integers by zero is undefined, this definition has meaning only if "a" and "b" are both different from zero. However, some authors define lcm("a",0) as 0 for all "a", which is the result of taking the lcm to be the least upper bound in the lattice of divisibility.