Ovary is half-inferior in the flowers of

When the gynoecium is situated in the centre and the other floral parts are located on the rim of the thalamus at almost the same level, the flower is perigynous and the ovary is half-inferior.
Examples of perigynous flowers: plum, rose and peach.
Cucumber and guava have epigynous flowers with an inferior ovary.
Brinjal has a hypogynous flower with a superior ovary.
Hence the ovary is half-inferior in plum.