, the unit of molality
, or concentration
per unit mass
One molal = 1 mole per kilogram.
The word molal does not have a separate symbol, so
1 molal = 1 mol/kg
However, m may be used for molality, and so in effect as a symbol for molal.
Also used as the adjective in talking about molal concentration. This is opposed to molar concentration, which is amount per unit volume.