envelope

enveloppe

Pochette plate en papier où l'on met une lettre ou une carte, notamment pour l'envoyer par la poste.

En anglais simple : A flat paper cover that holds a letter or card, especially when you send it by post.

• Put the letter in an envelope.
• She wrote my address on the envelope.
• Who sent this empty envelope?

Expressions courantes : sealed envelope, open an envelope, envelope address, paper envelope

enveloppe

Couche ou couverture extérieure qui entoure complètement quelque chose.

En anglais simple : A layer or outer cover that surrounds something completely.

• A protective envelope surrounds the cell.
• The balloon’s envelope was filled with hot air.
• The planet has a thin envelope of gas.

Comment l'utiliser : an envelope of something (An envelope of hot gas surrounds the star.)

Synonymes : covering, outer layer

Expressions courantes : outer envelope, protective envelope, envelope of gas

domaine de fonctionnement, domaine de vol

Limites dans lesquelles une machine ou un système peut fonctionner correctement et sans danger.

En anglais simple : The limits within which a machine or system can work safely and properly.

• The aircraft stayed within its flight envelope.
• Engineers tested the motor’s operating envelope.
• Flying outside the envelope can damage the aircraft.

Comment l'utiliser : within/outside the envelope (The pilot kept the aircraft within its flight envelope.)

Synonymes : operating limits

Expressions courantes : flight envelope, operating envelope, performance envelope