Lieutenant, junior grade

Lieutenant, Junior Grade is a junior commissioned officer rank of the UNSC Navy, equal in rank to First Lieutenant in the UNSC Marine Corps, UNSC Air Force, and UNSC Army.

Style of address

 * Lieutenants, Junior Grade are referred to as "Lieutenant" in informal settings.
 * Lieutenant, Junior Grade can be abbreviated as "Lieutenant (J.G.)" or "LTJG".

Trivia
Preston Cole was likely a Lieutenant, Junior Grade when he was aboard the UNSC Las Vegas during the Callisto Incident. Though he is referred to as a "Second Lieutenant," that is not a Navy rank, therefore he was most likely a Lieutenant, Junior Grade.