In the true and proper meaning of the terms […] every word handed down in every human language is an arbitrary and conventional sign: arbitrary, because any one of the thousand other words current among men, or of the tens of thousands which might be fabricated, could have been equally well learned and applied to this particular purpose; conventional, because the reason for the use of this rather than another lies solely in the fact that it is already used in the community to which the speaker belongs.
- Whitney (1875), a pag.19

The essential difference, which separates man’s means of communication in kind as well as degree from that of the other animals, is that, while the latter is instinctive, the former is, in all its parts, arbitrary and conventional.
- Whitney (1875), a pag.282