The Agron (Hebrew: האגרון) was Saadia Gaon's first production, completed in his twentieth year (913). The book is also known by its Judeo-Arabic name 'אצול אלשער אלעבראני' (the Rudiments of Hebrew Poetry). The Agron compiled by Saadia Gaon is not a Hebrew language dictionary, per se, that defines the different meanings of a certain word, or of a certain radical (Hebrew stem, or root), but rather a lexicographical reference book for payṭanim which includes in its first section words whose first letters are arranged in alphabetical order, for use in making acrostics at the beginning of the poetic line; whereas in the second section are listed words whose last letters (syllables) are arranged in alphabetical order, for use in making rhymes at the end of the poetic line. The work consists of two parts, and was intended to be used in versification, in which acrostics and rhyme were the chief requisites. In a later edition, Saadia added the Arabic translation of each word, and also included passages concerning various "memorable subjects of the poets," and named the work in its new form "Kitab al-Shi'r." The Arabic introduction to the second edition and the Hebrew preface of the first have been in great part preserved (see Harkavy, "Studien," v. 39-59).