Every grammatical sentence conveys one leading idea with its modifications and relations.

Now a Chinese would express these latter by unconnected syllables, the precise bearing of which could only be guessed by their position; a Greek or a German would use independent words, indicating their relations by terminations meaningless in themselves; an Englishman gains the same end chiefly by the use of particles and by position.

Very different from all these is the spirit of a polysynthetic language.

It seeks to unite in the most intimate manner all relations and modifications with the leading idea, to merge one in the other by altering the forms of the words themselves and welding them together, to express the whole in one word, and to banish any conception except as it arises in relation to others.

Thus in many American tongues there is, in fact, no word for father, mother, brother, but only for my, your, his father, etc.