Sentence:  The dialect in which these writings are composed goes usually by the name of the <WSD>Zend</WSD> ; it is also styled the<!-- "the" sic --> Avestan, and sometimes the<!-- "the" sic --> Old Bactrian, from the country Bactria, the north-easternmost region of the great Iranian territory, which is supposed to have been its specific locality. 
Meaning of the word marked with <WSD> tags:  The Avestan language.