What term describes the process of approximating a number by rounding up or down based on a cutoff digit?

The process of approximating a number by rounding up or down based on a cutoff digit is best described as rounding. Rounding involves adjusting the number to the nearest specified place value, which can either be a whole number, decimal, or fraction, depending on the context. When rounding, you look at the digit immediately following the cutoff digit to determine whether to round up (increase the value of the cutoff digit by one) or round down (leave the cutoff digit as is).

For example, if you are rounding the number 4.6 to the nearest whole number, you would look at the digit in the tenths place (6). Since 6 is 5 or greater, you round up to 5. Conversely, if you were rounding 4.3, you would round down to 4. This clear distinction in the process specifically aligns with the concept of rounding rather than simply estimating, approximating, or calculating, which are broader terms that do not specifically denote the action of adjusting based on a cutoff digit.