Englishfor English speakers
open
Verb
—
To move something to the side to allow entrance.
I will open the door for our guests.
—
To prepare for business.
She opened the store.
open
Adjective
—
Having a hole or opening, not closed.
The door was open.
—
Available for business.
The shop is open.
an
Determinative
—
An (or a) is used when the following word could be any of a certain type.
I just ate an apple.
It is indeed an honor to have met you today.
envelope
Noun
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An envelope is a paper cover that you put a letter in to send it.
She put the letter into the envelope, addressed it to Charles, and put a stamp on it.
—
An envelope is a covering that goes all the way around something.
Each virus has a special envelope of protein surrounding it.