work of cohesion per unit area 

https://doi.org/10.1351/goldbook.W06688
Of a single pure liquid or solid phase α, wCα is the work done on the system when a column α of unit area is split, reversibly, normal to the axis of the column to form two new surfaces each of unit area in contact with the equilibrium gas phase. wCα=2 γα where γα is the surface tension between phase and its equilibrium vapour or a dilute gas phase.
Source:
PAC, 1972, 31, 577. (Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry) on page 597 [Terms] [Paper]