In the Middle Ages a number of Armenian dictionaries were written, most of which are known to modern science. However, there are also dictionaries which are not so famous; they were published, for instance, in the 17th century Armenian books. Among these dictionaries, we should mention the one written by Vardan Yownanean and published in 1674. Vardan Yownanean tanslated Johannes Bona’s religious work from Latin into Armenian and attached a dictionary consisting of 50 pages at the end of the translation. The author wanted to make Latin words as well as some Armenian words created by him understandable, in order to make his translation more easily readable.  Younanian explained the meaning of many words in his dictionary by using words of popular speech as well as dialectical words; he created many new terms and explained them. For instance, he created the Armenian equivalents for such Latin words as Promptus, Histrio, Larva, Discriptio. Not all the words created by the author were later used but they have great importance for the study of the Armenian language's history. The given article presents the peculiarities of the dictionary, the complete list of the newly-formed words.