en
ve
lope
复数形式
envelopes
1
信封, 封套
a thin, paper cover in which we put and send a letter
- He wrote the address on the envelope.
他把地址写在信封上。
- I need to buy some envelopes for my Christmas cards.
我需要为我的圣诞卡买一些信封。
- She found an old envelope with photos in it.
她发现了一个里面有照片的旧信封。
- She handed me an envelope with a note inside.
她递给我一个里面有便条的信封。
- The envelope contained a surprise birthday card.
信封里有一张惊喜的生日贺卡。
2
信封, 包装
any wrapper or covering
3
4
包络线, 操作上限
the maximum operating capability of a system (especially an aircraft)
5
包膜, 覆盖物
a natural covering (as by a fluid)
6
包络线, 包络
a curve that is tangent to each of a family of curves