wetness

Wetness is the state of being covered or saturated with a liquid, typically moisture such as water, on a surface or within a material. It describes both a physical condition and a perceptual experience: physically, it depends on how well a liquid spreads and adheres to a surface; perceptually, it is how wetness feels to touch and how evaporation cools the skin.

In physics, wetting refers to the affinity of a liquid for a solid and is quantified by interfacial tensions at the liquid–gas–solid interface. The contact angle formed by a liquid droplet on a surface indicates wettability: small or zero contact angles mean good wetting and spreading, while large angles indicate poor wetting and droplet formation. Surface tension, liquid properties, surface roughness, and the presence of contaminants or surfactants all influence wetting behavior.

Perception of wetness involves tactile and thermoreceptive cues. Mechanoreceptors sense moisture and texture, while thermoreceptors detect cooling from evaporation, together creating the sensation of wetness even if a surface may not be heavily coated.

Wetness is related to, but distinct from, moisture measurements such as humidity or moisture content, which quantify water in the air or in a material rather than the surface spread of a liquid. In practical contexts, wetness affects coating and printing performance, textile care, corrosion, and biological processes like dew formation and plant leaf wetting.