In the US and several other western forces, officers in training are referred to as student officers, and carry the rank of Cadet ( the Army, and Air Force) or Midshipman (in the Navy and in some countries, Marines). These officers may be serving at a military academy, or (as common in the United States), as members of a military training unit attached to a civilian college or university, such as an ROTC unit. This is due to a common requirement that comissioned officers have at least a four-year degree. The British Army refers to its trainee officers as Officer Cadets (OCdt), who hold no authority over other ranks (except when appointed to carry out a role as part of training). OCdts are refered to as Mister/Miss until the completion of the early stages of their training, thereafter non-officers will refer to him/her as Sir/Ma'am.
http://en.wikipedia.org/wiki/Military_rank#Subordinate.2FStu...

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Note added at 3 ore (2010-01-18 11:38:39 GMT)
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Sangro are dreptate! Cadetul e elev la scoala de ofiteri iar plutonierul nu e ofiter. M-am cam grabit:)
Am găsit insă ceva cu care sper sa-mi rascumpar greşeala:
http://en.wikipedia.org/wiki/Private_(rank)