Is it correct to say:
1) I forgot to bring my English book. (Does this mean my English text book or a book written in the English Language). Is it better to say, I forgot to bring my English Language book.
2) I forgot to bring my Economics book.
3) In school, we always say, I forgot to bring my maths but it sounds funny if I say I forgot to bring my economics.
1 It is more likely to be your English Language book. It could be a book written in English, but it would imply that you only had one book in English, and from the context, I would assume that you meant a book to study English. You could also use the word textbook or coursebook to make it absolutely clear.
3 To me, I forgot my maths means that I can't remember what I was taught- I would say maths book.