* Literal: I carefully placed the letter inside the envelope and sealed it with a kiss.
* Figurative: The envelope of secrecy surrounding the project was finally breached, and the news was leaked to the press.
* Technical: The engineers calculated the precise envelope of the aircraft's performance capabilities.
* Idiom: He felt the envelope of his comfort zone begin to stretch as he took on the new challenge.
* Humorous: The magician pulled a rabbit out of the envelope before revealing the real trick – a hidden trapdoor.