Process measure
Process measures measure parts of the system. They measure steps in the system to assess if a project or improvement effort is on track. Often process measures measure the activities you are doing to achieve an outcome, in an attempt to answer how an outcome is produced, rather than looking at the outcome itself.
Process measures are often part of a family of measures in quality improvement efforts along with Outcome Measures and Balancing Measures.
See: Science of Improvement: Establishing Measures from the Institute for Healthcare Improvement