contact angle

https://doi.org/10.1351/goldbook.C01290
When a liquid does not spread on a @S06084@ (usually a solid), a contact @A00346@(\(\theta \)) is formed which is defined as the @A00346@ between two of the interfaces at the three-phase line of contact. It must always be stated which interfaces are used to define \(\theta \). It is often necessary to distinguish between the 'advancing contact @A00346@' (\(\theta _{\text{a}}\)), the 'receding contact @A00346@' (\(\theta _{\text{r}}\)) and the 'equilibrium contact @A00346@' (\(\theta _{\text{e}}\)). When \(\theta _{\text{r}}\neq \theta _{\text{a}}\) the system is said to exhibit contact @A00346@ @H02930@
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 598 [Terms] [Paper]