Mail:

You're referring to the postal service!

Here are some common uses of the word "mail":

1. Sending letters or packages: "I'm going to mail this letter to my friend."
2. Electronic mail: "I need to send an email to my boss."
3. Postal service: "I'm going to the post office to mail a package."
4. Mailbox: "I need to check my mailbox for any new letters or bills."

Some other related words you might find useful:

• Post: "I'm going to the post office to send a package."
• Envelope: "I need to put this letter in an envelope before I mail it."
• Stamp: "I need to buy a stamp to mail this letter."
• Package: "I'm going to mail this package to my sister."

Let me know if you have any other questions or if there's anything else I can help you with!