An abecedarium (or abecedary) is an
inscription consisting of the letters of the
alphabet, almost always listed in order. Typically, abecedaria (or abecedaries) are practice exercises.Some abecedaria include obsolete letters which are not otherwise attested in inscriptions. For example, abecedaria in the
Etruscan alphabet from Marsiliana include the letters B, D, and O, which indicate sounds not present in the
Etruscan language and are therefore not found in Etruscan inscriptions. Others, such as those known from
Safaitic inscriptions, list the letters of the alphabet in different orders, suggesting that the script was casually rather than formally learned.
See more at Wikipedia.org...