Definition of adsorbate?

An adsorbate is a substance that is adsorbed onto the surface of another substance, typically a solid or liquid. Adsorption is the process by which molecules or particles adhere to the surface of a material, rather than being absorbed into it. Adsorbates can include gases, liquids, or solids that are attracted to and adhere to the surface of a solid or liquid material.

Adsorbate is the substance that is being adsorbed onto the surface.