Kidney disease, also known as nephropathy or renal disease, is damage to or disease of a kidney. Nephritis is inflammatory kidney disease. Nephrosis is noninflammatory nephropathy. Kidney disease usually causes kidney failure (renal failure) to more or less degree, with the amount depending on the type of disease. In precise usage, disease denotes the structural and etiologic disease entity whereas failure denotes the dysfunction (lack of working well, that is, impaired renal function); but in common usage these meanings overlap; for example, the terms chronic kidney disease and chronic renal failure are usually considered synonymous. Acute kidney disease has often been called acute renal failure, although nephrologists now often tend to call it acute kidney injury.