envelope

信封、封套

She sealed the envelope and wrote the address on the front.

她封好信封，在正面寫上地址。

外膜、包覆層、外殼

The seeds are protected by a thin envelope of jelly.

這些種子外面有一層薄薄的膠質外膜保護。

極限、界限、範圍多用於 push the envelope

The new engine design pushes the envelope of fuel efficiency.

這款新引擎的設計把燃油效率推向極限。

突破極限、挑戰極限

Their latest album really pushes the envelope of electronic music.

他們最新的專輯真的突破了電子音樂的極限。