A term used in Reliability Centered Maintenance. The secondary functionality required of an asset - generally not associated with the reason for acquiring the asset, but now that the asset has been acquired, the asset is now required to provide this functionality. For example a secondary function of a pump may be to ensure that all of the liquid that is pumped is contained within the pump (i.e.. the pump doesn't leak). An asset may have tens or hundreds of secondary functions associated with it.