Fair use
The American right to use copyrighted material without permission, decided case by case with a four-factor test.
The doctrine grew out of 19th-century US case law and was codified in the Copyright Act of 1976. Courts weigh the purpose of the use, the nature of the work, how much was taken, and the effect on the market for the original. "Transformative" use – making something new rather than a copy – counts for a lot. The upshot is flexible and therefore unpredictable: you find out it was fair use when the ruling comes down.
Fair use saved Google Books in 2015 and Android in Oracle v. Google in 2021, and the same four factors are where the fights over training AI on copyrighted text are now being fought. Sweden and the rest of the EU have no equivalent, just an enumerated list of exceptions such as quotation and private copying.