[…] all the languages in question [Romanic and Germanic tongues] are the divaricated representatives of a single tongue, spoken somewhere and some when in the past by a single limited community, by the spread and dispersion of which all its discordances have in the course of time grown up. Such a grand congeries of related languages, in different degrees, we are accustomed to call a “family:” a name taken, by an allowable figurative transfer, from the vocabulary of genealogy.
- Whitney (1875), a pag.174

[…] it is the first task of the comparative study of languages to divide all human speech into families […].
- Whitney (1875), a pag.228-229

[…] linguistic scholars have hitherto been able to put together into families only those languages which have a common structure. That is to say, only tongues which have shared at least a part of their growth out of the original radical stage (provided they have left it) have yet been found to exhibit reliable evidence of relationship.
- Whitney (1875), a pag.229

[…] the vast majority of languages have been grouped together by their affinities into families and branches of families […].
- Whitney (1875), a pag.174-175

[…] there is not a language in the world which does not exist in the condition of dialectic division, so that the speech of each community is the member of a more or less extended family- unless, indeed, there may be here and there an isolated language so nearly extinct as to be used only by the narrowest possible community: by a few families or a single village.
- Whitney (1875), a pag.175

It is […] only when the structure and material of the families shall have become understood with equal thoroughness, by the bringing to bear of all the evidences lying within the boundaries of each, that apparent resemblances between them can be deemed genuine, or used as signs of original connection. It is not enough that such preparatory work be done in one family; all the subjects of comparison must be reduced to the same value before they can be treated as commensurable.
- Whitney (1875), a pag.314

We have called a certain body of languages a family, the Indo-European. The name “family” […] was applied to it by strict analogy with the use of the same term elsewhere: the languages in question had been found, on competent examination, to show good evidence of descent from a common ancestor.
- Whitney (1875), a pag.228