What does the notation "kg kg-1" for units mean for specific humidity I am using a data set from Justin Sheffield at Princeton that includes specific humidity. The description is as follows:


  "Reanalysis 6-hourly specific humidity interpolated to 1.0deg with account for elevation changes and scaled to maintain consistency with reanalysis relative humidity and CRU TS3.0 monthly air temperature";
  The units are = "kg kg-1"


What does this mean? Does it mean kg/kg so essentially dimensionless? Because I have seen around specific humidity measured also in g/kg, maybe that was wrong? 
These two pages give the same definition of specific and absolute humidity, I thought they were different things: 
http://www.nzifst.org.nz/unitoperations/drying3.htm
http://tigge.ecmwf.int/tigge/d/show_object/table=parameters/name=specific_humidity/levtype=pl/
Yes, the unit is kilogram per kilogram, but it means kilogram of water (moisture) per kilogram of air.