(i) Litmus is the adsorbate and charcoal is the adsorbent.
(ii) The material providing the surface upon which absorption occurs, is known as the adsorbent and the substance adsorbed is called adsorbate.
(iii) The process of removal of adsorbed substance from the surface of the adsorbent is called desorption.
(iv) The phenomenon in which absorption and adsorption occur together is called sorption.