A thank you letter is a formal or informal note written to express gratitude and appreciation for a specific action, favor, or opportunity. It is commonly used in professional settings, such as after a job interview, receiving a gift, or receiving support in a project. The letter typically acknowledges the kindness or help, conveys genuine appreciation, and may reiterate the sender’s interest in continuing the relationship or collaboration. A well-written thank you letter leaves a positive impression, demonstrates professionalism, and strengthens personal or professional connections. It is a simple but powerful way to show appreciation and foster goodwill.