J21 or J-21 may refer to:
Vehicles
Aircraft
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Junkers J 21, a German reconnaissance aircraft
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SAAB J 21, a Swedish fighter
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Shenyang J-21, a Chinese prototype fighter
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Soko J-21 Jastreb
The Soko J-21 ''Jastreb'' (from sr-Cyrl, јастреб, translation=hawk), referred to as the J-1 ''Jastreb'' in some sources, is a SFR Yugoslavia, Yugoslav single-seat, single-engined, light attack aircraft, designed by the Aeronautical Techn ...
, a Yugoslav light attack aircraft
Locomotives
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LNER Class J21, a British steam locomotive class
Ships
* , a ''Bangor''-class minesweeper of the Royal Navy and Royal Canadian Navy
* , an ''Östergötland''-class destroyer of the Swedish Navy
* , a survey ship of the Indian Navy
Other uses
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Bronchiolitis
Bronchiolitis is inflammation of the small airways also known as the bronchioles in the lungs. Acute bronchiolitis is caused by a viral infection, usually affecting children younger than two years of age. Symptoms may include fever, cough, run ...
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County Route J21 (California)
There are 45 routes assigned to the "J" zone of the California Route Marker Program, which designates county routes in California. The "J" zone includes county highways in Alameda, Calaveras, Contra Costa, Fresno, Kern, Inyo, Mariposa, Mer ...
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Elongated pentagonal rotunda
In geometry, the elongated pentagonal rotunda is one of the Johnson solids (''J''21). As the name suggests, it can be constructed by elongating a pentagonal rotunda (''J''6) by attaching a decagonal prism to its base. It can also be seen as an el ...
, a Johnson solid (J
21)
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