A megasporophyll, almost always at the center of a flower, its margins more or less fused together or with other carpels to enclose the ovule(s). [source: APweb:Glossary]
In some cases, a gynoecium (PO:0009062) may consist of only one carpel, in which case annotations should go on carpel (PO:0009030). The word pistil is used synonymously with gynoecium, but if a gynoecium consists of a single carpel, then pistil may be used synonymously with carpel. If carpels are fused, the gynoecium is a syncarpous gynoecium, as in Poaceae, Brassicaceae and Solanaceae. If carpels are free, the gynoecium is an apocarpous gynoecium, as in Fabaceae. If you are annotating to this structure for Zea mays or other grasses, please also add an annotation to the corresponding floret type. Choose the most specific term possible from: spikelet floret (PO:0009082), ear floret (PO:0006354), upper floret of pedicellate spikelet of ear (PO:0006350), upper floret of sessile spikelet of ear (PO:0006352), tassel floret (PO:0006310), upper floret of pedicellate spikelet of tassel (PO:0006314), upper floret of sessile spikelet of tassel (PO:0006316).