There are some exceptions to this sound change, although they are rare. They include ("haha" "mother", expected form "hawa"), ("hoho" "cheek", expected form "hō"), ("ahiru" "domestic duck", expected form "airu"), and ("afure-ru" "overflow", expected form "aore-ru" or "ōre-ru". Sometimes, as in the case of the first two exceptions, the sound change form exists, usually with a slightly different meaning ( "hawa" is a hyper-formal and very respectful term for mother) or is used in different contexts ( "hō" is generally used in isolation, while "hoho" is generally used in compounds). In other cases, as is true of the second two exceptions, the unchanged form is the only one that exists. In addition to these exceptions, some dialects may preserve these sounds as they were at any stage of the language.