Pushing something too far.
9 and if you really want to push the envelope 10 ...just a little humor....10
It means you are stretching the borders. You are doing things with something that wasn't originally intended to be done.
Envelope in this case is an aeronautic (aircraft and piloting) term for the limits in which it's safe to operate the aircraft. "Pushing the envelope" means doing something just a little bit harder/faster etc than what's considered safe and sensible.
The answer is an envelope. It contains a letter.
The word is "envelope" (which usually holds only one letter).
It does
Envelope is a noun.
The possessive form for the noun envelope is envelope's.Example: The envelope's flap wasn't sealed.
The prepositional phrase in the sentence is "on the envelope".
This envelope is like the window envelope,but the window opening is uncovered (an uncovered address panel).
on the envelope.
When sending a wedding invitation the response card should go into the response envelope and you should address it back to you on the front of the response envelope with a stamp on the envelope.