I slid the letter into the envelope.
She posted her job application in a rose-scented envelope.
She ripped open the envelope, expecting to find money in the birthday card. She was thoroughly disappointed.
She got the card and put it into the envelope and then put it in with the birthday present.
That is a rather thick envelope. The ship began to slowly disappear as the fog bank began to envelope it.
The postage stamp on the envelope was colorful.
The word its is a possessive form of the pronoun 'it', used as an attributive adjective.It is less awkward than saying 'Put the letter in the letter's envelope' or '... the envelope of the letter'.
Please send a self-addressed envelope to our office.
I opened the envelope that contained my check.
Sealing usually means, to be encasing something in an envelope or another object, so a good sentence would be:When sealing an envelope, make sure that it is pressed down firmly.
the cells have a nuclear envelope.
He sent a remittance to his family overseas to help with their living expenses.
When an envelope is marked, "confidential", we're not authorized to open it; give it directly to the manager.
The envelope and its portentous contents fell onto the mat with a dull thud.
The Greek word for "Envelope" is "φάκελος".
The prepositional phrase in the sentence is "on the envelope".