Correct structure of $\mathrm{\gamma }$-methylcyclohexane carbaldehyde is

Aldehydes and ketones are often called by their common names instead of IUPAC names. The common names of most aldehydes are derived from the common names of the corresponding carboxylic acids  by replacing the ending –ic of acid with aldehyde. At the same time, the names reflect the Latin or Greek term for the original source of the acid or aldehyde.

The location of the substituent in the carbon chain is indicated by Greek letters α, β, γ, δ, etc. The α-carbon being the one directly linked to the aldehyde group, β carbon the next, and so on. 

In the above structure methyl group is attached to the $\mathrm{\gamma }$  Position to the aldehyde group.It has a cyclohexane ring

$\mathrm{\gamma }$-methyl cyclohexane carbaldehyde

The IUPAC name of the above compound is 3-Methylcyclohexanecarbaldehyde