8.It is commonly supposed that these two modes of expression are, in very many instances, equivalent to each other in meaning, and consequently interchangeable.

Were Sound and Form merely interchangeable symbols of some deeper uncataloged Reality?

All of the coins and bills were readily interchangeable with the United States coins in common use, the dollar being worth two pesos, the half dollar one peso, the twenty-five cent piece a half peso, the ten-cent piece a peseta, the five-cent piece a media peseta and the cent two centavos.

Which and that are seldom interchangeable; when they are, use that.