# Newton Law vs Newton’s Law [duplicate]

Do I need an apostrophe-s in reference to major concepts?

For example, I see both versions as in:

• Planck’s constant
• Planck constant

Are both forms considered correct?

At Wolfram Alpha, if you type in either Newton Law or Newton's Law, it assumes that you mean Newton's First Law. I regularly see the possessive form, but rarely see "Newton Law."

References to the value, h, are Planck Constant or Planck's Constant, 4.135688 * 10^(-15) electron-volt seconds. Wolfram calls it by the former, but Wikipedia uses either (but is titled by the former).

• I have only EVER heard Newton's law and Planck's constant. As I commented in the "possible duplicate" If you add The in front, you could make "The Planck constant" if you had to – mplungjan Dec 17 '13 at 16:08
• @mplungjan I've certainly heard "the Planck constant". – Jon Hanna Dec 17 '13 at 16:15
• Yes, I have only seen "Newton's Second Law." I saw "Planck's constant" in college texts, back when slide rules and dinosaurs ruled the earth. But I will bow to more contemporary usage on Wolfram Alpha. See wolframalpha.com/input/?i=planck+constant&lk=4&num=1. – rajah9 Dec 17 '13 at 16:19
• books.google.com/ngrams/… – mplungjan Dec 17 '13 at 18:21
• @mplungjan, I am seeing "Planck's constant" peaking around 1961, while "Plank constant" is rising more slowly, but only reaching one-third the level of "Planck's". Is that what you're seeing, also? – rajah9 Dec 17 '13 at 18:40

Newton's law refers to a law made by Newton. Planck constant refers to a constant named after Max Planck.

The National Institute of Standards and Technology names h Planck constant. You could name it NIST's Planck constant if you want to speak about it in contrast to the way other people defined it.

The National Institute of Standards and Technology provides the official name for the Planck constant and Planck's constant seems to be an obsolete term that's still in use.

Additional there's a "Newtonian constant of gravitation" instead of a "Newton constant of gravitation". As a result you probably would want to use the Newtonian law if you speak about someone's reformulation of Newton's law. You also have Newtonian physics instead of Newton physics or Newton's physics.

• Great reference, simultaneously disturbing. NIST is recommending new constants for G, h, Avogadro's number, and others, based on further research and uncertainties. Avogadro constant is in the eighth decimal place; gravitational constant in the fifth. It's a shame that the physicists and chemists can't have unwavering constants, like pi and e. – rajah9 Dec 17 '13 at 18:54