A UAV is a flying machine with no pilot inside it. Someone controls it from the ground, or it flies itself by following a plan and using GPS. The letters stand for Unmanned Aerial Vehicle. The everyday word for the same thing is 'drone' — that is what almost everyone says in normal talk. 'UAV' is the formal word: you meet it in the army, in engineering reports, in news about war, and in rules made by governments. So a soldier's report says UAV; a shop selling one to you says drone. UAVs range from a small four-propeller toy you hold in one hand, up to a machine as big as a real plane. They are used to look at things from above — watching an area, taking photographs, mapping land, checking crops or power lines — and some military ones also carry weapons. You say the three letters separately: U-A-V. It is a countable noun: one UAV, two UAVs. You will also meet 'UAS' (Unmanned Aircraft System), which means the aircraft plus the controller and the ground equipment all together, and some official writing now prefers 'uncrewed' to 'unmanned'.