almagest
noun
al·ma·gest ˈal-mə-ˌjest 
: any of several early medieval treatises on a branch of knowledge
Word History
Etymology
Middle English almageste, from Anglo-French & Medieval Latin, from Arabic al-majusti, the Arabic version of Ptolemy's astronomy treatise, from al the + Greek megistē (syntaxis), literally, greatest (composition)
First Known Use
14th century, in the meaning defined above