Definition
Risk severity is the measure of how serious the consequences of a hazard would be if the associated risk were realized, ranging from negligible (minor inconvenience) through minor, major, hazardous, and catastrophic (loss of aircraft or life). It is one of the two components used in risk assessment, the other being likelihood (probability of occurrence).
Plain English
Severity answers the question: if this goes wrong, how bad would it be? It rates the worst outcome a hazard could cause, from a minor nuisance up to a fatal accident.
Context Anchor
Used when assessing flight risks before or during a flight, especially when deciding whether a condition is acceptable, needs a control, or should stop the flight.
Derivation
From Latin severus, meaning 'serious' or 'strict.' Severity describes how serious the outcome is — not how often it happens. Pairing this with the word's origin helps separate it cleanly from likelihood.
Why Pilots Care
It determines how aggressively a risk must be mitigated even when probability appears low.
Grounding Statement
If the possible outcome could seriously injure people, damage the aircraft, or cause loss of control, the risk severity is high even if the situation does not happen often.
Intuition Check
Risk severity does not mean the same thing as the overall risk level. It answers only one question: if this goes wrong, how bad could the result be?
Example Sentence 1
The instructor explained that the severity of a midair collision is catastrophic, which is why even a low likelihood demands strong mitigations like traffic scanning and ADS-B.
Example Sentence 2
Even with low probability, the high risk severity of engine failure after takeoff required an immediate return to the airport.