No, a building wing is not called an "ewl." The term "ewl" does not refer to any architectural feature; it is likely a misspelling or confusion with the word "wing" itself. In architecture, a "wing" typically refers to a part of a building that extends from the main structure, often used to house different functions or spaces.
The phrase building wing refers to a specific section of a building. A building that is shaped like an L would have 2 different wings.
A building's extension is a wing. As in, "The hospital is adding a wing". Or, "They named it 'The Gonzo Wing' because Gonzo funded it".
If you mean the side arms of a church, it is called "the transept". Each of the two may contain a chapel.
West Wing
It is just called the wing.
If you are referring to the distance from wing tip to wing tip, it is usually called "wingspan".
the wing flap
Annex
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The White House
it's a part of a building designated for remixing tunes, often referred to as "the remix wing". example: Where is Dave? Oh, he's over in the remix wing.
It's called delta wing because the wing is shaped like the Greek letter delta: Δ.