Avogadro's law
Concise Oxford English Dictionary © 2008 Oxford University Press:
Avogadro's law /avəˈɡɑːdrəʊz/ (also Avogadro's hypothesis)
▶noun Chemistry a law stating that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.
'Avogadro's law' also found in these Oxford entries:

