[…] there is no absolute dividing-line between what is material and what is formal in a language; material and form are relative words only, names for degrees, for poles of a continuous series, of which the members shade into one another. And […] the grandest movement in a growing and improving language is that from more material to more formal uses, whereby both words and phrases take on a less gross and physical meaning, even to the extent of being attenuated into form-words, or, in combination with other elements, into formative elements- both alike indicators of relation.
- Whitney (1875), Pag. 222