Envelop, with no final e, is the verb meaning to surround or wrap up completely. Envelope, with the final e, is the noun for the paper cover you post a letter in. Memory hook: the extra e sits on the thing you can hold, the envelope.
The core difference
Envelop is the verb for surrounding or enfolding; envelope is the noun for a paper cover or an operating limit.
- envelop — to surround or enfold: Fog began to envelop the entire valley by nightfall.
- envelope — a paper cover for letters, or a safe operating limit: She sealed the invitation inside a cream-coloured envelope.
How to tell them apart
Envelop is the action word and is pronounced with the stress on the second syllable, en-VEL-up. Envelope is the object, most often the flat paper cover for a letter, and it can also mean the limits within which something, such as an aircraft, can safely operate.
The confusion is common because envelope is sometimes used as a verb by mistake. As a verb meaning to surround, the standard spelling is envelop. If you can put a letter in it, add the e.
