See: surface tension
Sources:
Green Book, 2nd ed., p. 12 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
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 596 (https://doi.org/10.1351/pac197231040577)