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c.1400, from medical Latin, from Greek oidema (genitive oidematos) "a swelling tumor," from oidein "to swell," from oidos "tumor, swelling," from PIE *oid- "to swell;" cf. Latin aemidus "swelling," Armenian aitumn "a swelling," Old Norse eista "testicle," Old English attor "poison" (that which makes the body swell), and the first element in Oedipus.
edema e·de·ma (ĭ-dē'mə)
n. pl. e·de·mas or e·de·ma·ta (-mə-tə)
An accumulation of an excessive amount of watery fluid in cells, tissues, or serous cavities.