Lieutenant Junior Grade

Lieutenant Junior Grade (often abbreviated to Lieutenant JG, Lt.JG or simply JG) is a military rank, the equivalent of which is used by the service organizations of many civilizations. As a traditional naval grade, Lieutenant Junior Grade is the second most junior line officer rank.

Use in Starfleet

The Starfleet rank of Lieutenant Junior Grade sits between the ranks of Ensign and Lieutenant. The rank is equivalent to the rank of First Lieutenant which is used by Starfleet's Marine Corp.

An Ensign's primary duty is professional growth, both as a leader and as an occupational specialist. Ensigns are mentored by more senior officers as well as their (nominally) subordinate Chief Petty Officers as part of their development as Starfleet officers. As a Ensign proves themselves more capable, they are considered for promotion into the Lieutenant tier. On some of Starfleet's larger starship classes like the Galaxy and Sovereign Classes of starships, it is not uncommon for veteran and seasoned enlisted personnel to have Ensigns working for them as technicians, thus having the Ensign "learning the ropes" of the more technical aspects of their job.

Advancement

A Starfleet Officer will usually spend anywhere from a year to several as a Ensign. Advancement to the Lieutenant tier is dependant on several factors, this varies from personal and career development, to their position in the fleet and even to their chosen specialties.