Physical Law
Law
noun
It's both a law and a rule. This usually refers to something that is a physical law, but also can simply be a law, too. Anyways, lots of rules. Lots of laws. It's both, so the stronger one (law) takes precedence.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
うーん、六才の子に、重力の法則を教えるいい方法ってありますか？
Hmm, is there a good way to teach a six-year-old about the law of gravity?
そのベーコンは、自然の法則によってマミに食べられた。
That bacon was eaten by Mami according to the law of nature.
もしウサギが高速で走っている電車の車内で真っすぐ上に飛び跳ねても、慣性の法則によって同じ場所に着地することになります。
If a rabbit jumps straight up in the cabin of a high speed train, according to the law of inertia, it will land in the same place.