Hypothesis: a tentative explanation of some regularity of nature

   Law:               a concise general  statement (verbal or mathematical)
                           on natural phenomena.

   Theory:         a unifying principle that explains a body of fact.

Avogadro's Hypothesis  ->  Avogardo's Law
First Law of Thermodynamics,
Boyle's Law, Coulomb's Law, Ohm's Law
Phlogiston Theory,  Ether Theory :  Defunct
Ionic Theory (of Solutions),
Transition State Theory (of Chemical Reaction Rates)
Theory of Relativity