Oedema
Edema is the discharge of serous fluid from the vascular system and its accumulation in the tissue (tissue clefts of skin or mucous membrane), but also in nerve tissue, in the interstitium of parenchymatous organs; furthermore intercellular and interfibrillary. It's a volume increase in the interstitial tissue fluid, partly also of the intracellular space, due to venous backwater or in case of disturbances of the electrolyte balance and the acid-base equilibrium.
In clinical everyday life, the term oedema is used primarily to describe the swelling of the tissue, perceptible fluid accumulations in the subcutis or fluid accumulations in certain organs (e.g. pulmonary and cerebral oedema).