Frequency

1.The number of occurrences per unit time (e.g. per year).[12]

2.It is the number of occurrences of an event per unit time. In QRA, it is usually expressed as the frequency per year. [ARF Document]

3.The number of occurrences per unit time (e.g. per year). [IACS ]

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Sources
1. IACS International Association of Classification Societies LTD
10. ARF Document The exact reference is not provided.
12. MSC/Circ.1023-MEPC/Circ.392 Formal Safety Assessment

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