The alkaline hydrolysis of a fat or oil with aqueous sodium hydroxide to give soap is called

Heating a triglyceride with aqueous NaOH breaks the three ester linkages and gives sodium salts of fatty acids plus glycerol. This process is called saponification. Esterification is the reverse type of bond formation, hydrogenation adds $\mathrm{H}{}_2$ and sulphonation introduces $-\mathrm{SO}{}_3\mathrm{H}$.