Simplify the following text for a Grade 9 native English-speaking person.
Original: The Treaty on the Non-Proliferation of Nuclear Weapons , also Nuclear Non-Proliferation Treaty ( NPT or NNPT ) is a treaty to limit the spread ( proliferation ) of nuclear weapons .
Simplified: The Nuclear Non-Proliferation Treaty ( or NNPT ) is a treaty that was made to stop nuclear weapons from being built .