An example of a morphophonological alternation in English is provided by the plural morpheme, written as "-s" or "-es". Its pronunciation varies among , , and , as in "cats", "dogs", and "horses" respectively. A purely phonological analysis would most likely assign to these three endings the phonemic representations , , . On a morphophonological level, however, they may all be considered to be forms of the underlying object , which is a morphophoneme realized as one of the phonemic forms }. The different forms it takes are dependent on the segment at the end of the morpheme to which it attaches: the dependencies are described by morphophonological rules. (The behaviour of the English past tense ending "-ed" is similar: it can be pronounced , or , as in "hoped", "bobbed" and "added".)