IUPAC name of the structure, $\mathrm{HOOC}-\mathrm{CH}\left(\mathrm{OH}\right)-{\mathrm{CH}}_2-\mathrm{CH}\left(\mathrm{CHO}\right)-{\mathrm{CH}}_2-{\mathrm{CH}}_3$ is

IUPAC name of the structure, $\mathrm{HOO}\stackrel{1}{\mathrm{C}}-\stackrel{2}{\mathrm{C}}\mathrm{H}\left(\mathrm{OH}\right)-\stackrel{3}{\mathrm{C}}{\mathrm{H}}_2-\stackrel{4}{\mathrm{C}}\mathrm{H}\left(\mathrm{CHO}\right)-\stackrel{5}{\mathrm{C}}{\mathrm{H}}_2-\stackrel{6}{\mathrm{C}}{\mathrm{H}}_3$is  4 - formyl - 2 - hydroxy hexanoic acid ;

-COOH is the principal functional group.

-CHO and -OH groups are treated as substituents.

Alphabetical order is followed for naming ;