A thank-you note is a written message expressing gratitude to someone for a gift, favor, or kind gesture. It can be sent in various forms, such as a handwritten card, an email, or a text message. Thank-you notes are often used in personal and professional settings to acknowledge the thoughtfulness of others and strengthen relationships. Typically, a thank-you note includes a specific mention of what the sender is grateful for, such as a birthday gift or help with a project. It is a simple yet meaningful way to show appreciation and can leave a positive impression on the recipient.