1. The difference between a computed, observed, or measured value or condition and the true, specified, or theoretically correct value or condition. For example, a difference of 30 meters between a computed result and the correct result. 2. An incorrect step, process, or data definition. For example, an incorrect instruction in a computer program. 3. An incorrect result. For example, a computed result of 12 when the correct result is 10. 4. A human action that produces an incorrect result. For example, an incorrect action on the part of the programmer or operator.