A structural principle of language and its implications

Sentence qualifier markers, like those indicating interrogation and negation, are placed before verbs in consistent VO languages, after verbs in consistent OV languages. This placement principle permits us to identify other sentence qualifiers, like potential, desiderative, and reflexive. It also provides means for distinguishing qualifier markers from congruence as well as deixis markers. Moreover, it has morphological and phonological implications, leading to so-called agglutinative structure. Besides contributing to our understanding of linguistic structure, this principle enables us to clarify some problems in the historical development of languages.