Can one use already said sentences as examples on a language lesson?

Question

Suppose I teach English (at school or I'm a private teacher, or I'm writing a book, or I'm creating an app - the point is that people pay me). In my teaching materials I give examples of correct sentences written in English. In the world there are correct English sentences which are already said or written: in books, in songs, in vlogs, in the comments on StackExchange.

Can I use such sentences (in the written form) in my teaching materials without asking permission to or paying anyone? If so, must I put the source of the sentence? Let's assume I'd just take one sentence from one context (1). I'd like to spread my teaching materials internationally. Are there any catches?

(1) I mean that, for example, I wouldn't write "We are the champions, my friend. We'll keep on fighting till the end", I would write at most one of these sentences.

Answer 1

If you're in the USA, this almost certainly falls under fair use, or if you are in another jurisdiction, it almost certainly falls under an analogous exception for educational use. The fact that the excerpt is short contributes to this conclusion.

You can also avoid having to rely even on these exceptions by choosing sources that are in the public domain. The specific date before which a work is guaranteed to be in the public domain depends, again, on your jurisdiction, but it's probably sometime in the early 20th century. For example, you're certainly on solid ground if you use Dickens.

Answer 2

In the US this might well fall under fair use, depending on the exact details. Whether something is fair use or not always depends on the facts, and no one factor is final. That this is being used for an educational purpose would tilt toward fair use. If the amount of any one source used is small compared to the full size of the source that would also help, and if there is no plausible harm to the market for the original (if there is any such market) that would also favor fair use.

In a number of countries include the UK there is a legal concept known as fair dealing which is somewhat similar to fair use, but different in detail, and generally more limited. In some countries that have neither fair use not fair dealing there is an exception to copyright for limited educational use, which might apply in the situation described.

When text (or an image) is used under a claim of fair use, it is normal to attribute it, indicating the source, but this is not an absolute requirement of fair use. Still providing source information would probably help any fair use claim.