•DESs were introduced as an alternative to ILs to overcome their drawbacks.•Some authors consider DESs as a subclass of ILs.•DESs and ILs share many properties which allow them to be used in many fields of analytical chemistry.•It is very bad practice to consider ILs and DESs terms interchangeable. Deep eutectic solvents (DES) were introduced as an alternative to ionic liquids (IL) to overcome the drawbacks of IL solvents. However, some authors consider them to be a subclass of ILs. In contrast, other authors emphasize that these are by their nature independent, different groups of substances. Thus, the question arises: Which solvent group should DESs belong to? Maybe a new class should be added to the existing ones. The aim of this work is to attract the attention of researchers using DES in their studies to the need for a proper use of terms.