A potential serious injury or fatality (PSIF) is an incident or near miss that did not cause a serious injury but could reasonably have done so under slightly different circumstances.
PSIF classification asks what could have happened, not what did. A forklift that passes a pedestrian at walking pace with room to spare is a near miss with low potential; the same pass at full speed with the pedestrian inside the truck’s path is a PSIF event, because the energy involved could have killed. Many sites screen every incident and near miss with a short set of questions about the energy source, the controls that were in place and how close the person came.
PSIF differs from SIF, which is an actual serious outcome, and from a SIF precursor, which is a standing condition rather than an event. Counting PSIF events gives a larger data set than counting SIFs, so trends show up sooner and investigation time goes to the events that matter. The PSIF full form and meaning article explains the classification in more detail.