The equivalence of the four hydrogen atoms of methane rested on indirect evidence, e.g.
Equivalent terms, which are not necessarily identical or literal translations, were adopted for the English, French and German languages, the equivalence being closest and most systematic between the English and German terms.
A special algebra is one which differs from ordinary algebra in the laws of equivalence which its symbols obey.
A simple class of cases is that which deals with equivalence of sums of money in different currencies; these cases really come under § 120.
For in the latter case we possess, according to Hume, no standard of equivalence other than that supplied by immediate observation, and consequently transition from one premise to another by way of reasoning must be, in geometrical matters, a purely verbal process.