 One of the largest sources of complexity in morphology is that this one-to-one correspondence between meaning and form scarcely applies to every case in the language.In English, there are word form pairs like "ox/oxen", "goose/geese", and "sheep/sheep", where the difference between the singular and the plural is signaled in a way that departs from the regular pattern, or is not signaled at all.Even cases regarded as regular, such as "-s", are not so simple; the "-s" in "dogs" is not pronounced the same way as the "-s" in "cats"; and, in plurals such as "dishes", a vowel is added before the "-s".