To preserve the proper vowel sounds, scholars developed several different sets of vocalization and diacritical symbols called "nequdot" (, literally "points"). One of these, the Tiberian system, eventually prevailed. Aaron ben Moses ben Asher, and his family for several generations, are credited for refining and maintaining the system. These points are normally used only for special purposes, such as Biblical books intended for study, in poetry or when teaching the language to children. The Tiberian system also includes a set of cantillation marks, called "trope" or , used to indicate how scriptural passages should be chanted in synagogue recitations of scripture (although these marks do not appear in the scrolls). In everyday writing of modern Hebrew, "niqqud" are absent; however, patterns of how words are derived from Hebrew roots (called "shorashim" or "triliterals") allow Hebrew speakers to determine the vowel-structure of a given word from its consonants based on the word's context and part of speech.