Contact angle
= Contact angle
{title2=$\theta_c$}
The contact angle is measured through a liquid between its interface and a solid substrate at their contact line. In a gently sloping two-dimensional film on a horizontal substrate, its small-angle value is the limiting magnitude of the height slope. A zero contact angle means a tangential approach to the substrate; it does not imply bounded curvature, as the limiting <zero-flux thermocapillary film profiles> illustrate.