envelope

American  

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

noun

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.

---

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

---

Etymology

Origin of envelope

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

Example Sentences

Just that morning his uncle had complained to his aunt that he couldn’t get an envelope he needed because it was in the den where the boy was sleeping.

From Literature

I hurried back to the room, plucking an envelope out of my backpack.

From Literature

"We wanted to really push the envelope on how we can provide an even greater spotlight for the players, these magnificent athletes, on the court, that effectively becomes their stage," Tiley added.

From BBC

Bold and daring looks often push the envelope.

From Los Angeles Times

“AI is really pushing the envelope for performance and reliability,” Yang said, adding that some chip customers are planning around materials that haven’t even been invented yet.

From MarketWatch

Related Words

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