Look up: U

1. 
   u
   a common replacement for the Greek letter µ as a symbol for the micron or micrometer. The correct symbol for this unit is µm.
   Found on http://www.unc.edu/~rowlett/units/dictU.
   
   
2. 
   U
   a commercial unit of thermal conductance (heat flow). The U factor, as it is also called, is the conductance through an insulator as measured in Btu's of energy conducted times inches of thickness per hour of time per square foot of area per °F of temperature difference between the two sides of the material. The U factor is numerically equal t...
   Found on http://www.unc.edu/~rowlett/units/dictU.
   
   
3. 
   U
   a unit of distance used to measure the height of the standard racks in which audio, video, or computer components are mounted. 1U is equal to 1.75 inches (44.45 millimeters), so that, for example, a 2U component is 3.5 inches high, and a 22U rack houses a stack of components 38.5 inches high.
   Found on http://www.unc.edu/~rowlett/units/dictU.
   
   
4. 
   U
   usual symbol for the enzyme unit.
   Found on http://www.unc.edu/~rowlett/units/dictU.
   
   
5. 
   U
   German symbol for a turn or revolution (Umdrehung), usually seen in combinations such as U/min, the German equivalent of the English symbol rpm for revolutions per minute.
   Found on http://www.unc.edu/~rowlett/units/dictU.
   
   
6. 
   U
   U, 21st letter of the alphabet, corresponding to the Greek upsilon [Gr.,=u without the aspirate]. Until the late Middle Ages the capital was V, the minuscule u, no distinction being made between the consonantal and vocalic uses of the letter. The fixing of modern orthography, however, has restricted...
   Found on http://www.infoplease.com/ce6/society/A0
   
   
7. 
   U
   U, honorific used in Myanmar. See second part of name (e.g., Thant, U).
   Found on http://www.infoplease.com/ce6/history/A0