A refrigerator (often called a "fridge" for short) is a cooling appliance comprising a thermally insulated compartment and a mechanism to transfer heat from it to the external environment, cooling the contents to a temperature below ambient. Refrigerators are extensively used to store foods which deteriorate at ambient temperatures; spoilage due to bacterial growth and other processes is much slower at low temperatures. Devices described as "refrigerators" maintain a temperature a few degrees above the freezing point of water; similar devices which maintain temperatures below the freezing point of water are called "freezers". The refrigerator is a relatively modern invention amongst kitchen appliances. It replaced the common icebox which had been a household item for almost a century and a half prior, and is sometimes still called by the original name "icebox".