I am working on a language app to learn languages, and I was thinking to include sentences and dialogues for the users to practice their languages. My question is: can I re-use, and to what extend, similar exercises used in other textbooks? Does that fall under the fair use for educational purpose?
And more in particular, I am wondering about the following 3 cases:
Are vocabulary lists for specific lessons copyrighted? I know a single word (e.g. in Latin) + translation in English is not copyrighted, but what about whole series of words as vocabulary list? E.g.: can I add to the "lesson 1" of my app the vocabulary list at the end of chapter one of a hypothetical book "learn Latin in 20 lessons"?
What about dialogues, especially very basic ones, like "What is your name? My name is Paul. Where are you from? I am from Canada"? are they copyrighted? or it depends, and how can I determine the threshold?
The app will focus mainly on ancient, dead languages, like Latin. I guess that sentences taken from ancient texts can be used freely as exercises. But what about basic sentences created by the author of a teaching book to illustrate specific examples? Or sentences from the initial exercises, which often are made up to illustrate specific grammatical concepts? Are those sentences copyrighted, or again could I use the sentences of the exercise at the end of chapter one of the same hypothetical book "learn Latin in 20 lessons" ?