What is the difference between "liquid water content" and "absolute humidity" in meteorology? Both have units of mass/volume.
According to the online chapter Water Vapor (University of British Columbia), the two variables you ask about are defined as:
Liquid water content
The main difference is that absolute humidity measures the mass of water vapour and the LWC measures the mass of suspended or falling liquid water content in a unit volume of air. A handy definition linking the two terms is (from the linked document):
LWC is the liquid-water analogy to the absolute humidity for water vapor.