Hahaha. This is something I have repeated what seems like a million times.
Here are some common phrases I hear from students:
- When will you back to Australia?
- I backed to my home on the weekend.
- I want to back your book
This is really strange English! これは変な英語ですよ！
Now, for correct English you can easily replace “back” with “return”.
- When will you return to Australia?
- I returned to my home on the weekend.
- I want to return your book
Now, you can also use “back” in these sentences, but you must also use a verb.
- When will you go back to Australia?
- I went back to my home on the weekend.
- I want to give back your book
- Put my dictionary back in the drawer.
「BACK」は動詞ではありません！！
OK? 
