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A comforter (in American English), also known as a doona in Australian English, or a continental quilt (or simply quilt) or duvet in British English, is a type of bedding made of two lengths fabric or covering sewn together and filled with insulative materials for warmth, traditionally down or feathers, wool or cotton batting, silk, or polyester and other down alternative fibers. Like quilts, comforters are generally laid over a top bed sheet (and sometimes also blankets). Duvets are another form of quilt, traditionally filled with feathers, though since the late 20th century often made of synthetic fibres or down alternatives.
A comforter is sometimes covered for protection and prolonged use. Comforter covers are similar in principle to pillowcases, usually closed with zippers or buttons.
In the United Kingdom the term comforter is not generally used. It is instead called a quilt, duvet or an eiderdown. A duvet differs in that it is thicker and usually used without blankets or extra sheets.
Sometimes a comforter is sold as a "bed in a bag". This term usually denotes an entire set of bedding, including either a comforter or duvet with its cover.
The terminology comforter comes from the word comfort. Comforters are usually used in the winter season when it is very cold. Due to the thickness of a comforter or the amount of down/feathers or other filling it has, a person is insulated against cold.
Comforter sizes correspond with bed sizes: twin, full, queen, king, and cal-king. Comforter sizes run slightly larger than mattress sizes to allow for draping over the sides of the bed. Typical sizes in the United States for comforters are:
- Twin = 64" (163 cm) width × 87" (221 cm) length
- Queen / Full = 87" (221 cm) width × 87" (221 cm) length
- King = 101" (257 cm) width × 90" (229 cm) length.
Filling - Comforters are filled with layers of natural material such as down feathers, wool, or silk, or polyester batting. Comforters can also be made out of fur, usually with a backing of satin or silk. The loft of the filling determines the weight as well as the level of insulation. The comforter is stitched or quilted to secure the filling and keep it evenly distributed. 
Shell/Covering - The outer shells of comforters are typically made with cotton, silk, or polyester fabrics or blends, of varying thread counts. Comforter shells vary in design and color, often designed to coordinate with other bedding.
- Down Comforter Guide. Retrieved November 11th, 2016, from http://comfortersetguide.com/down-comforter-guide.html