The science to which the process applies will alter the definition of absorption slightly. For example if you are referring to a chemical process, absorption is the process by which one substance, such as a solid or liquid, takes up another substance, such as a liquid or gas, through minute pores or spaces between its molecules. Consider a sponge or some other wiping tool. They take up water, and the water takes carbon dioxide. In biology the movement of molecules through semipermeable membranes through osmosis is considered absorption. In physics it is the taking up and storing of energy like sound, light, and etc. without being transmitted in some way.
Adsorption on the other hand, is the process by which molecules of a substance, such as a gas or a liquid, collect on the surface of another substance, such as a solid. The molecules are attracted to the surface but do not enter the solid's minute spaces as in absorption.
Adsorption, the taking up by the surface of a solid or liquid (adsorbent) of the atoms, ions, or molecules of a gas or other liquid (adsorbate). Porous or finely divided solids can hold more adsorbate because of the relatively large surface area exposed. Similarly, the adsorbent surface of a quantity of liquid is increased if the liquid is divided into fine droplets. In some cases, the atoms of the adsorbate share electrons with atoms of the adsorbent surface, forming a thin layer of chemical compound. Adsorption is also an important part of catalysis and other chemical processes. Absorption occurs when the molecules of adsorbate penetrate the bulk of the solid or liquid adsorbent.
Absorption, in physics, the taking up of energy by matter. All around us there are many sources of energy; the sun, light bulbs, room heaters. This energy, however, may be absorbed or diminished by other bodies. Absorption of energy is the reduction in the amount of energy available to allow a body to do work. The energy is not lost but rather converted to some type of internal energy within the absorbing medium. The control of the rate of absorption of energy is important in many areas such as regulating temperatures within ovens and noise reduction by muffling sound. Radiation in the form of streams of high-energy particles such as electrons and other radio-active particles can also be absorbed by high density material such as lead. The absorption of such radioactivity is clearly important for safety reasons.