First lieutenant
A commissioned officer in the army, air force, or marine corps ranking above a second lieutenant and below a captain [Merriam-Webster’s Dictionary].
A naval officer is responsible for a ship's upkeep [Merriam-Webster’s Dictionary].
First Lieutenant is the second junior commissioned officer rank after Second Lieutenant and is generally awarded as an automatic promotion to Second Lieutenants who have served for 18 to 24 months. First Lieutenants may serve as the Platoon Leader of a specialized weapons platoon or as the executive officer of a company consisting of 70 to 250 soldiers. Some officers receiving a promotion to First Lieutenant may receive a further promotion to higher ranks with more leadership responsibility [Military-ranks.org].
First Lieutenant is the 20th rank in the United States Army, above Second Lieutenant and below Captain. A first lieutenant is a Commissioned Officer at DoD pay grade O-2, with a starting monthly pay of $4,007 [Military-ranks.org].
First lieutenant. Noun. Merriam-Webster's Dictionary. Retrieved from: https://www.merriam-webster.com/dictionary/first%20lieutenant
O-2 First Lieutenant - Commissioned Officer - U.S. Army Ranks. Military-ranks.org. Retrieved from: https://www.military-ranks.org/army/first-lieutenant