 It is often claimed that there are elements of the grammar which are not found in these language families.Frequently mentioned is Esperanto's agglutinative morphology based on invariant morphemes, and the subsequent lack of ablaut (internal inflection of its roots), which Zamenhof himself thought would prove alien to non-Indo-European language speakers.Ablaut is an element of all the source languages; an English example is "song sing sang sung."