(美亦作 sincerely yours)a formula used to end a letter, typically a formal one in which the recipient is addressed by name你诚挚的（信末署名前的套语，多用于以名字称呼收信人的正式信函中）
柯林斯高阶英汉双解学习词典释义
ADV-GRADED
真诚地;诚实地
If you say or feel something sincerely, you really mean or feel it, and are not pretending.
In Britain, people write 'Yours sincerely' before their signature at the end of a formal letter when they have addressed it to someone by name. In the United States, people usually write 'Sincerely yours' or 'Sincerely' instead.