Amazon has a feature called "Kindle Books Lending" that allows Kindle users to loan eligible Kindle books to friends and family for up to 14 days. Here is a step-by-step guide on how to loan books on Amazon:
Go to the Amazon website and log in to your account.
Find the book you want to loan on your Kindle Library.
Click on the "Actions" button next to the book title, then select "Loan this book."
Enter the recipient's email address and an optional personal message.
Click on "Send now" to send the loan request.
The recipient will receive an email with instructions on how to accept the loan. Once they accept the loan, they will have 14 days to read the book before it automatically returns to your library.
Note that not all Kindle books are eligible for lending, and some publishers may choose to opt-out of lending for specific titles. Also, you can loan a book only once, and you can't access the book while it's on loan.
It's worth mentioning that if you own a physical book, and you would like to lend it to someone, you can use the Amazon Prime Reading feature, that allows you to borrow one book per month for free.
Overall, lending Kindle books on Amazon is a simple process that allows users to share their favorite books with friends and family without having to physically give away their own copy.