The process whose specific outcome is the progression of the tongue over time, from its formation to the mature structure. The tongue is the movable, muscular organ on the floor of the mouth of most vertebrates, in many other mammals is the principal organ of taste, aids in the prehension of food, in swallowing, and in modifying the voice as in speech. [ http://purl.obolibrary.org/obo/UBERON_0001723 GOC:jl ]