By Formal letters, Constructions

If you know the name of the person you are addressing - e.g. if you started the letter Dear Mr... then you should end the letter Yours sincerely,... If you do not know the letter of the person you are addressing - e.g. if you started the letter Dear Sir or Madam or To Whom It May Concern, you...

It's sometimes called "telegraphic style" - as if you were sending a telegram and paying for each word, you would leave out some words to make it shorter. You might write like this in a diary, or in a very informal letter, especially if almost every sentence would otherwidse begin with "I." In...