Complex sentence: The imperial and US customary systems of measurement are two closely inter-related systems of measurement both derived from earlier English system of measurement units which can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.
Split into simpler sentences: The imperial and US customary systems of measurement are two closely inter-related systems of measurement, imperial units and United States customary units. They are both derived from the English system of measurement units which can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.