A letter of thanks, letter of gratitude, thank you card, or thank you letter is a letter or greetings card that is used when one person/party wishes to express appreciation to another. They are frequently sent after an event (a birthday party, a religious festival or holiday) and especially when a gift has been received.[1] Personal thank-you letters and cards are often hand-written and the addressee is typically a friend, acquaintance or relative. Letters of gratitude are usually written as formal business letters, either to a client, a supplier, an employer (or prospective employer after an interview)[2] or an employee as part of creating an engaged workforce.[3]