all the nonzero digits of a number and the zeros that are included between them or that are final zeros and signify accuracy: The significant digits of 0.01230 are 1, 2, 3, and the final 0, which signifies accuracy to five places.

The digits in a decimal number that are warranted by the accuracy of the means of measurement. Significant digits are all the numbers beginning with the leftmost nonzero digit, or beginning with the first digit after the decimal point if there are no nonzero digits to the left of the decimal point, and extending to the right. For example, 302, 3.20, and 0.023 all have three significant digits.