surface tension, γ, σ

https://dx.doi.org/10.1351/goldbook.S06192
Work required to increase a surface area divided by that area. When two phases are studied it is often called interfacial tension.
Source:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 995