- noun a rank in the armed forces below a captain
- noun someone whose job is to help an important person
- noun a junior officer in the army or marines (equivalent to a first lieutenant in the US Army; usually in command of a platoon or equivalent-sized grouping)
- noun a junior officer in the navy, below lieutenant-commander
Information & Library Science
Origin & History of “lieutenant”
Etymologically, a lieutenant is someone who ‘holds the place’ of another (more senior) officer – that is, deputizes for him. The word comes from French lieutenant, a compound formed from lieu ‘place’ and tenant (source of English tenant). Lieu (borrowed independently by English as lieu (13th c.) in the phrase ‘in lieu of’) comes in turn from Latin locus ‘place’, source of English local. Locum tenens (17th c.) (or locum for short) ‘temporary replacement’, literally ‘holding the place’, is thus a parallel formation with lieutenant. Spellings of lieutenant with -f-, indicating the still current British pronunciation /lef-/, first appear as early as the 14th century.