If a gynoecium has a single carpel, it is called monocarpous. If a gynoecium has multiple, distinct (free, unfused) carpels, it is apocarpous. If a gynoecium has multiple carpels "fused" into a single structure, it is syncarpous.

When carpels are free they called what?

The female reproductive part of the flower is known as gynoecium. This gynoecium contains one or more carpels which develop into a fruit. If a gynoecium has a single carpel, it is called monocarpous and if the gynoecium has multiple, free and unfused carpels it is called apocarpous.

When more than one carpel is present they may be free and are called as?

When more than one carpel is present, they may be free (as in lotus and rose) and are called apocarpous. They are termed syncarpous when carpels are fused, as in mustard and tomato. After fertilisation, the ovules develop into seeds and the ovary matures into a fruit. called free central.