Truncation otherwise referred to as truncating a number is a method of approximating a decimal number by dropping all decimal places past a certain point without rounding. In other terms truncation is limiting the number of digits right of the decimal point. For instance, with pi (π), 3.14159265…, it can be truncated down to 3.1415. In this case, if 3.14159265...were rounded to the same decimal place, the approximation would result in the number 3.1416.
An analogue of truncation can be applied to polynomials. In this case, the truncation of a polynomial P to degree n can be defined as the sum of all terms of P of degree n or less. For instance, Polynomial truncations arise in the study of Taylor polynomials.
With computers, truncation can occur when a decimal number is typecast as an integer. In this case the number getting typecast is truncated to zero decimal digits because integers cannot store non-integer real numbers.
“Truncation.” Wikipedia, Wikimedia Foundation, 18 Dec. 2019, en.wikipedia.org/wiki/Truncation.