A self-addressed envelope is an envelope with your address on the front of it in the MAIL TO area. If the ad/directions include SASE...this means self-addressed stamped envelope. In this case, you would include postage so the company/organization/person can mail your request to you.
The answer is an envelope. It contains a letter.
Envelope is a noun.
It does
The word is "envelope" (which usually holds only one letter).
on the envelope.
This envelope is like the window envelope,but the window opening is uncovered (an uncovered address panel).
The prepositional phrase in the sentence is "on the envelope".
The possessive form for the noun envelope is envelope's.Example: The envelope's flap wasn't sealed.
When sending a wedding invitation the response card should go into the response envelope and you should address it back to you on the front of the response envelope with a stamp on the envelope.
Envelopes is correct.
I opened the envelope that contained my check.
When addressing a standard envelope, the correct location for the return address is the upper left corner of the envelope.