The contact angle is the angle formed between a liquid droplet and a solid surface at the point of contact. It measures how well a liquid wets a surface; a smaller angle indicates better wetting, while a larger angle suggests poor wetting. This property is important in various fields, including materials science and biology. Contact angles are influenced by factors such as surface energy and the chemical composition of the solid. For example, a droplet on a hydrophobic surface, like Teflon, will have a high contact angle, while on a hydrophilic surface, like glass, the angle will be much lower.