A digit that is nonzero, or when it is zero, it is followed only by zero digits. Used in rounding
any digit of a number that is known with certainty; any digit of a number beginning with the leftmost non-zero digit and ending with the rightmost non-zero digit (or a zero considered to be the exact value); "he calculated the answer to four significantfigures
(Computers) digit that has the highest value within a group of digits (according to which one can discover if the digit is written from left to right or vice-versa)