Fly has 27 different meanings across 4 categories:
Noun · Verb · Adjective · Proper Noun
two-winged insects characterized by active flight
"The mosquitoes swarmed around the porch lights as soon as dusk fell, buzzing with their characteristic rapid wing beats."
fisherman's lure consisting of a fishhook decorated to look like an insect
"The angler carefully tied his new mayfly imitation onto the line before casting it into the still water."
Any insect of the order Diptera; characterized by having two wings (except for some wingless species), also called true flies.
"The insect's wings beat rapidly against the glass window."
The action of flying; flight.
A wing.
In plain English: A fly is a small insect with big wings that buzzes around and often lands on food.
"The fly buzzed around my ear all afternoon."
Usage: Use "fly" as a noun to refer to a small insect with wings, not the insect's wing itself. Do not use it to mean a single wing, as that would be grammatically incorrect in standard English.
display in the air or cause to float
"fly a kite"
"All nations fly their flags in front of the U.N."
travel over (an area of land or sea) in an aircraft
"Lindbergh was the first to fly the Atlantic"
To travel through the air, another gas, or a vacuum, without being in contact with a grounded surface.
"The center fielder sprinted back just in time to catch the fly before it touched the grass."
To hit a fly ball; to hit a fly ball that is caught for an out. Compare ground (verb) and line (verb).
In plain English: To fly means to move through the air by using wings or an aircraft.
"We flew to Paris for our vacation."
Usage: In baseball, to fly means to hit a high pop-up that is easily catchable, whereas to ground means to hit the ball along the ground and to line means to hit it sharply into the air at a downward angle. Use fly only when describing this specific type of high, vertical trajectory resulting in an out if caught.
(British informal) not to be deceived or hoodwinked
"If you think I'm going to pay full price for that second-hand jacket, you're barking mad because I've got my eyes wide open and won't fly."
Quick-witted, alert, mentally sharp.
"She was so fly that she spotted the mistake in the contract before anyone else noticed it."
In plain English: Fly describes something that is very fast, exciting, and impressive to watch.
"The fly screen on the window was torn, letting bugs into the room."
Usage: Use "fly" to describe someone who is quick-witted, alert, and mentally sharp in conversation or problem-solving. Avoid using this term for physical speed, as that requires the adverb "quickly" or the adjective "fast."
A surname.
"My neighbor, Mr. Fly, always greets me with a cheerful wave as he walks his dog."
The word "fly" comes from Old English flȳġe, which originally meant the insect we know today. It traveled into English through Middle English and is related to similar words for the insect in many other Germanic languages.