Structure of 4 - Methylpent - 2 - enal is:

"4-Methyl" indicates that there is a methyl group (${\mathrm{CH}}_3$) attached to the fourth carbon atom.

"Pent-2-enal" indicates that there is an aldehyde functional group ($─\mathrm{CHO}$) attached to the  five-carbon chain, and there is a double bond ($─\mathrm{C}=\mathrm{C}─$) between the second and third carbon atoms.