envelope

封筒

手紙やカードを入れる平たい紙の袋。特に郵送に使う。

やさしい英語で： 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?

よく使う表現： sealed envelope, open an envelope, envelope address, paper envelope

外被、外膜

物を完全に包んでいる層や外側の覆い。

やさしい英語で： 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.

使い方： an envelope of something (An envelope of hot gas surrounds the star.)

類義語： covering, outer layer

よく使う表現： outer envelope, protective envelope, envelope of gas

動作範囲、飛行包絡線

機械やシステムが安全かつ正常に働ける範囲。

やさしい英語で： 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.

使い方： within/outside the envelope (The pilot kept the aircraft within its flight envelope.)

類義語： operating limits

よく使う表現： flight envelope, operating envelope, performance envelope