A gynoecium (from Ancient Greek gyne, "woman") is the female reproductive part of a flower. The male counterpart of is called an androecium. A gynoecium is composed of one or more pistils. A pistil may consist of a single free carpel, in which case the gynoecium is termed monocarpous. A pistil can also be formed from a number of carpels that are fused, and in this case the flower is synocarpous. "Apocarpous" refers to two or more distinct carpels. The pistil itself is formed from the stigma, style, and ovary. See carpel for a longer discussion.
A plant ovary (much like an animal ovary) is the part of the pistil which contains ovules. The style is generally referred to as stalklike, without ovules located between the ovary (at the bottom of the pistil) and the stigma (located at the top portion of the pistil). In some plant species styles are not found in the pistils. Stigma is the pollen receptor within the pistil at the top of the pistil. Stigmas may be discretely defined structures or they may be within a region referred to as the stigmatic region. 
- Simpson, M.G.: "Plant Systematics", pp. 374-375. Elsevier Academic Press, 2006