in a meaured value, the numbers that are known for certain, and the first uncertain measured value. In any experimental measurement there is a degree of uncertainty. To show just the meaningful number in any experimental result, use significant digits. For example, if you measure mass on a scale that is accurate to the nearest ±0.01 g, then a mass of 1.14 g is known to be 1.1 g for sure (these two digits are certain, but the .04 g is not sure so is the first uncertain digit. Thus this number has three significant digits. When doing calculations with experimentally measured values, the results must carry no more digits than the least accurately known value used in the calculation. Check here for more detailed information about significant digits.

The number of digits to consider when using measuring numbers. There are three rules in determining the number of digits considered significant in a number. 1) All non-zeros are significant. 2) Any zeros between two non-zeros are significant 3) Only trailing zeros behind the decimal are considered significant

the number of digits that are valid for a measurement.