O
O，Initial o in Pali may represent a Vedic o or a Vedic au （see ojas，ogha，etc．）．Or it may be guṇa of u （see oḷārika，opakammika，etc．）．But it is usually a prefix representing Vedic ava．The form in o is the regular use in old Pali； there are only two or three cases where ava，for metrical or other reasons，introduced．In post-canonical Pali the form in ava is the regular one．For new formations we believe there is no exception to this rule．But the old form in o has in a few cases，survived．Though o； standing alone，is derived from ava，yet compounds with o are almost invariably older than the corresponding compounds with ava （see note on ogamana）．（Page 162）