How to Spell envelope

envelope - noun

• A paper or cardboard wrapper used to enclose small, flat items, especially letters, for mailing.

• Something that envelops; a wrapping.

• A bag containing the lifting gas of a balloon or airship; fabric that encloses the gas-bags of an airship.

• A mathematical curve, surface, or higher-dimensional object that is the tangent to a given family of lines, curves, surfaces, or higher-dimensional objects.