Favorlang is an extinct Formosan language formerly spoken in the central-western plain of Taiwan. The few documents in it written by seventeenth century Dutch missionaries indicate some interesting features not commonly found in other Formosan or extra-Formosan languages. Favorlang was, no doubt, closely related to Babuza, which itself had died out by the end of the nineteenth century, before Japanese scholars had had a chance to investigate it in any detail. 
These Favorlang texts are the only source material for an understanding of the grammatical structure of the language. They are the more precious considering the fact that (in addition to Babuza) three other closely related western plains languages — Taokas, Papora, and Hoanya — had also gone extinct, but leave us with no recorded syntactic data for them. 
The introduction to our corpus provides a general background of the Favorlang language, describes the nature of the written documents, shows the problems of the Dutch orthography, discusses the linguistic position of Favorlang, and gives a sketch of Favorlang grammar, including its phonology, morphology, and syntax. 
There are fourteen short catechismic texts and Christian prayers and five longer sermons in Favorlang. The fourteen shorter texts are accompanied by Dutch translations, later translated into English by William Campbell, not including the five sermons. Peter Knecht worked out free translations for the five sermons, as based on the interlinear glosses by Naoyoshi Ogawa. This monograph provides both interlinear glosses and free translations for all nineteen items.