SIL

discrete level (one out of a possible four), corresponding to a range of safety integrity values, where safety integrity level 4 has the highest level of safety integrity and safety integrity level1 has the lowest

Note 1 to entry:  The target failure measures (see IEC 615084:2010, 3.5.17) for the four safety integrity levels are specified in Table 2 and Table 3 of IEC 615081:2010.

Note 2 to entry:  Safety integrity levels are used for specifying the safety integrity requirements of the safety functions to be allocated to the E/E/PE safety-related systems.

Note 3 to entry:  A safety integrity level (SIL) is not a property of a system, subsystem, element or component. The correct interpretation of the phrase “SIL n safety-related system” (where n is 1, 2, 3 or 4) is that the system is potentially capable of supporting safety functions with a safety integrity level up to n.

[SOURCE: IEC 615084:2010, 3.5.8]