envelope

American  

[en-vuh-lohp, ahn-] / ˈɛn vəˌloʊp, ˈɑn- /

noun

envelopes plural

1. a flat paper container, as for a letter or thin package, usually having a gummed flap or other means of closure.

2. something that envelops; a wrapper, integument, or surrounding cover.

3. Biology. a surrounding or enclosing structure, as a corolla or an outer membrane.

4. Geometry. a curve or surface tangent to each member of a set of curves or surfaces.

5. Radio. (of a modulated carrier wave) a curve connecting the peaks of a graph of the instantaneous value of the electric or magnetic component of the carrier wave as a function of time.

6. the fabric structure enclosing the gasbag of an aerostat.

7. the gasbag itself.

8. Electronics. the airtight glass or metal housing of a vacuum tube.

9. the technical limits within which an aircraft or electronic system may be safely operated.

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idioms

1. push the envelope, to stretch established limits, as in technological advance or social innovation.

envelope British  

/ ˈɒn-, ˈɛnvəˌləʊp /

noun

1. a flat covering of paper, usually rectangular in shape and with a flap that can be folded over and sealed, used to enclose a letter, etc

2. any covering or wrapper

3. biology any enclosing structure, such as a membrane, shell, or skin

4. the bag enclosing the gas in a balloon

5. maths a curve or surface that is tangent to each one of a group of curves or surfaces

6. electronics the sealed glass or metal housing of a valve, electric light, etc

7. telecomm the outer shape of a modulated wave, formed by the peaks of successive cycles of the carrier wave

8. informal to push the boundaries of what is possible

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Other Word Forms

Noun Inflected Forms

• envelopes
  plural

Etymology

Origin of envelope

1700–10; < French enveloppe, derivative of envelopper to envelop

Explanation

An envelope is something that envelops, or wraps around. It usually refers to the thing you stick a stamp on and snail mail. In the early 1700s, envelope, the noun for "wrapper," evolved from the French enveloppe, meaning “to envelop.” Envelope is always a noun, unlike the verb envelop which means “to wrap, cloak.” Synonyms for envelope range from casing and enclosure to pouch and sheath. Virginia Woolf said, “Life is a luminous halo, a semi-transparent envelope surrounding us from the beginning.” She ditched hers by walking into a river with her pockets full of rocks.

Example Sentences

When the reporter placed a letter for Paxton in the mailbox, an envelope addressed to Warren Paxton, the attorney general’s given name, was visible.

From Salon • Jul. 7, 2026

You and the person you’ve authorized to submit your mailed ballot must fill and sign the outside of the ballot envelope.

From Los Angeles Times • Jun. 2, 2026

"Every flight has pushed the boundaries of what's possible, steadily expanding the envelope and strengthening our confidence in the aircraft."

From Science Daily • Jun. 1, 2026

Historically, crypto has pushed the legal envelope, and may design rewards to mimic interest without violating the law.

From The Wall Street Journal • May 25, 2026

Mom takes an envelope out of her stuffed-full tote bag.

From "The Wrong Way Home" by Kate O’Shaughnessy

Related Words

• bag
• box
• casing
• coat
• container
• jacket
• pocket
• pouch