1. Anne's diary was published under the title of The Diary of a Young Girl.

2. Anne's diary was published under the title The Diary of Young Girl.

(Which one is correct? Do I have to write 'of' or not"?)

3. Did you write today's diary?
4. Did you write a diary today?
5. How about writing a diary now?
6. Will you write in a diary?
7. Will you write in today's diary?
8. Write three diaries about three days.
9. You have written two diaries, so you have to write the other diary on the notebook.

(Are all the expressions grammatical? would you correct the errors?)

The first one is correct: The Diary of a Young Girl

They're all correct -- except in # 9, we'd say IN the notebook.

1. The correct title is "The Diary of a Young Girl." In this case, the word "of" is necessary to indicate that it is a diary that belongs to a young girl named Anne.

2. The second statement is incorrect. It should be "The Diary of a Young Girl" with the word "of" included between "Diary" and "Young Girl."

3. The question "Did you write today's diary?" is grammatically correct. It refers to writing in a diary specifically for today.

4. The question "Did you write a diary today?" is also grammatically correct. It asks about any diary written on the day in question, without specifying if it refers to a specific diary.

5. The sentence "How about writing a diary now?" is grammatically correct. It suggests the idea of starting to write a diary at the present moment.

6. The question "Will you write in a diary?" is grammatically correct. It asks if the person will engage in diary writing in general, without specifying any particular diary.

7. The sentence "Will you write in today's diary?" is grammatically correct. It refers to writing in the diary that is specifically designated for today.

8. The sentence "Write three diaries about three days" is grammatically incorrect. It should be corrected to "Write three diary entries about three days." This suggests writing three separate entries, each representing a different day.

9. The sentence "You have written two diaries, so you have to write the other diary on the notebook" is grammatically incorrect. It should be corrected to "You have written two diary entries, so you have to write the third entry in the notebook." This states that two entries have been written and the third one needs to be completed in a notebook.