postscript, or p.s., for the more popular term
place something in an envelope together with a letter
A formal or causal letter is usually mailed in an envelope.
An envelope adressed to the recipiant of the intended letter
It means that there is something else included in the envelope, maybe another document, a picture or anything the sender wanted to include. Writing "enclosure" makes it clear to the recipient that there is something else in the envelope besides the letter to prevent the recipient from tossing something important in the garbage inadvertently.
On an informal letter, you do not usually include the address on the letter itself, only on the outside of the envelope.
The answer is an envelope. It contains a letter.
The word enclosure simply means that there is something else in the envelope besides the letter. Example: A cover letter for a resume that contains a letter of recommendation would tell the reader that a resume and letter of recommendation is also enclosed.
If you are including documents in addition to a letter in an envelope, the additional documents are called the enclosure(or enclosures).
it is a envelope.
The word is "envelope" (which usually holds only one letter).
Stamp, address, envelope, mailbox, mail carrier
The abbreviation SASE means 'Self Addressed stamped Envelope'. This is when you mail someone a letter and you want a response sent back so you include an envelope with a stamp on it and your address.