A den is a comfortable, usually secluded room in a house. In the United States, the type of rooms described by the term den varies considerably by region. It is used to describe many different kinds of bonus rooms, including studies, family rooms, home offices, libraries, home cinemas, or even spare bedrooms.

While living rooms tend to be used for entertaining company on formal occasions, dens, like other family rooms, tend toward the more informal. In houses that do not have dedicated family rooms or recreation rooms, a den may fill that niche. Dens can also be private areas primarily used by adult members of the household, possibly restricting access to the room by their children. Dens with home theater systems and large screen televisions may be referred to as media rooms instead. Most den floors are made out of wood, carpet or floor tiling.

Dens can serve the same purpose as cabinets in the past, becoming a modern man cave—a place for men to gather and entertain. In such cases, the design and decor may be distinctively masculine.

Den may refer to:

A room is any distinguishable space within a structure. Usually, a room is separated from other spaces or passageways by interior walls; moreover, it is separated from outdoor areas by an exterior wall, sometimes with a door. Historically the use of rooms dates at least to early Minoan cultures about 2200 BC, where excavations on Santorini, Greece at Akrotiri reveal clearly defined rooms within certain structures.

In early structures, diverse room types could be identified to include bedrooms, kitchens, bathing rooms, reception rooms, and other specialized uses. The aforementioned Akrotiri excavations reveal rooms sometimes built above other rooms connected by staircases, bathrooms with alabaster appliances such as washbasins, bathing tubs, and toilets, all connected to an elaborate twin plumbing systems of ceramic pipes for cold and hot water separately. Ancient Rome manifested very complex building forms with a variety of room types, including some of the earliest examples of rooms for indoor bathing. The Anasazi civilization also had an early complex development of room structures, probably the oldest in North America, while the Maya of Central America had very advanced room configurations as early as several hundred AD. By at least the early Han Dynasty in China (e.g. approximately 200 BC), complex multi-level building forms emerged, particularly for religious and public purposes; these designs featured many roomed structures and included vertical connections of rooms.

Sayumi Michishige (道重 さゆみ, Michishige Sayumi^?, (named after Sayumi Horie) born July 13, 1989 in Ube, Yamaguchi Prefecture, Japan) is a sixth generation member of the J-pop group Morning Musume and has the third longest tenure of any member in the group (behind Risa Niigaki and Ai Takahashi and tied with Reina Tanaka). As of May 18, 2012 right after Risa Niigaki's graduation, Tsunku announced on Ultra Smart 2012 concert that she is the new leader of Morning Musume.

She joined Morning Musume in 2003 along with Eri Kamei, Miki Fujimoto and Reina Tanaka, which all made their debuts with Morning Musume in the group's nineteenth single, "Shabondama". In 2005 she was assigned as mentor to 7th generation member Koharu Kusumi, until Kusumi's graduation in December 2009.

Michishige was also a member of the Hello! Project unit Ecomoni, along with former Morning Musume member Rika Ishikawa.

When Michishige passed the audition to join Morning Musume, Tsunku, Morning Musume's producer, commented that her singing was weak. After the audition, Michishige took voice lessons to improve her singing, but even she admits that her own singing is still bad.

Risako Sugaya (菅谷 梨沙子, Sugaya Risako^?, born April 4, 1994 in Kanagawa, Japan) is a Japanese pop singer, idol, and member of the musical group Berryz Kobo.

In 2002, Sugaya successfully passed the Hello! Project Kids Audition. Her debut within the Hello! Project world came with the premiere of the first Minimoni feature film, as part of 4Kids, a shuffles group formed exclusively for the movie.

In 2003, Sugaya starred in the movie Hotaru no Hoshi (蛍の星), as Hikari, a fragile elementary school student who, with the help of her caring teacher, has a chance to be momentarily reunited with her deceased mother and overcome her emotional problems. She also starred in the drama, Shonan Kawarayane Monogatari.

That year also marked her first appearance on Kōhaku Uta Gassen, as one of Aya Matsuura's backup dancers, during the 54th edition of the renowned NHK New Year program.

In early 2004, Sugaya became part of the newly formed group Berryz Kobo. Since joining the group, she has also participated in the band's weekly radio show Berryz Kobo Kiritsu! Rei! Chakuseki!.