So, now, how are the varieties of tone to be sorted out? How are the similarities and the differences among these many examples to be described and grouped? In connection with the main themes of Part Two, the pair "bet" and "wager" provides an interesting example. It is doubtful whether these two words differ, either in meaning or in use, in any of the ways discussed earlier. For the latter, The Concise Oxford Dictionary gives only the identity statement, "wager = bet". In The Shorter Oxford which, as we saw, includes among its style register the category "Formal", no mention is made of any special or restricted use for either word. So, are these two words perfectly synonymous? Are they everywhere interchangeable salva significatione? There is one colloquial or slang use that evidently does not permit substitution: the reply "You bet!", meaning "You may be sure". The implicit certainty of outcome suggests that it may be a shortened form of "You can bet (on it)". Another possibility is that it derives from the certainty of betting against oneself, as in "You bet you". Hence, perhaps, the slangy "You betcha" (sometimes "You bet ya"). Or maybe this expression is ultimately best viewed as idiomatic — a one-of-a-kind term that requires piecemeal learning. In which case it does not undermine the suggested synonymy.