1.When you write a letter,you should write the date at first and write your name at last;(写信在开头要写日期结尾要写名字,而作文不要)
2.An article has a title but a letter doesn't.（作文有题目而信件没有）
3.You should express your personal wishes when writing a letter while you needn't do so when writing an article.(写信时要表达自己的个人祝愿等,写作文不要)