an upper floor projecting from the rear over the main floor in an auditorium
"The audience members seated on the balcony had a clear view of the stage despite being elevated above the main floor."
a platform projecting from the wall of a building and surrounded by a balustrade or railing or parapet
"The family gathered on the balcony to enjoy the cool evening breeze while leaning against the iron railing."
An accessible structure extending from a building, especially outside a window.
"The family gathered on the small balcony that extended directly out of their bedroom window to enjoy the evening breeze."
In plain English: A balcony is an open platform sticking out from the side of a building that you can stand on to get fresh air or enjoy a view.
"She sat on the balcony to enjoy the fresh air and watch the sunset."
Usage: A balcony is an outdoor platform attached to the exterior of a building that projects outward and usually features a railing or balustrade. It differs from a terrace because it does not touch the ground directly but hangs over lower levels or streets below.
The word "balcony" comes from the Italian balcone, which originally meant a scaffold or floor-length window. It traveled into English through this Italian term rather than being borrowed directly for its current architectural sense.