An approximation is a result close enough for a practical purpose, though it is not exact. It may come from rounding, estimation, measurement, or a method designed to produce a near-value. Slide rules, for example, use aligned scales to estimate calculations rather than return calculator-level precision.
In cyber security, approximation can help analysts make quick estimates when exact data is unavailable or unnecessary—for example, judging likely risk or prioritizing alerts. It also matters when interpreting security tools: estimates, thresholds, and probabilistic detections should not be mistaken for certainty. Approximate results can guide decisions, but high-impact actions may require verification against more precise evidence.