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Lieutenant commander is a military rank, the equivalent of which is used by the service organizations of many civilizations.  

During the 23rd century, certain Lieutenant Commanders holding high shipboard positions, such as that of first officer, were authorized to wear the full braid insignia of a Commander while still retaining their rank of Lieutenant Commander. 
[[File:R-o4.png|left|thumb|Lieutenant Commander]]
In the 24th century Starfleet, Lieutenant Commander is an active rank with its close equivalents in alien militaries being the Cardassian rank of glinn and the Romulan rank of centurion. Lieutenant Commanders normally serve as senior department heads, executive officers on smaller vessels, and in some cases as starship commanders. Lieutenant Commanders Tom Markel, Jadzia Dax, and Piersall all held commanding officer postings.