Scytian language is the type of what is called an “agglutinative” structure, as distinguished from the “inflective” Indo-European. By this is meant that the elements of various origin which make up Scytian words and forms are more loosely aggregated, preserve more independence, than do the Indo-European; there is far less integration of the parts, with disguise and obliteration of their separate entity. All our own formations, as has been seen, begin with being agglutinations; and such words as ‘un-tru-th-ful-ly’ preserve an agglutinative character; if all our words were like it, there would be no marked difference between the two families as to this fundamental item.
- Whitney (1875), a pag.232

The Basque may […] be the sole surviving relic and witness of an aborigenal western European population, dispossessed by the intrusive Indo-European tribes […] It is of an exaggeratedly agglutinative type, incorporating into its verb a variety of relations which are almost everywhere else expressed by independent words.
- Whitney (1875), a pag.258-259

The wider distinction of languages as isolating, agglutinative, and inflective, which has a degree of currency and familiarity, offers a convenient, but far from exact or absolute, test by which the character of linguistic structure may be tried; the three degrees lie in a certain line of progress, but, as in all such cases, pass into one another. To lay any stress upon this as a basis of classification is like making the character of the hair or the color of the skin a basis of classification in physical ethnology, or the number of stamens or the combination of leaves in botany: it ignores and overrides other distinctions of an equal or of greater importance.
- Whitney (1875), a pag.277