"Ethnicity" is more similar to tribal identities - there are usually ways of entering the group, which can be well- or ill-defined. See for example the traditional initiation ceremonies of many Native American tribes for non-members, or the recently-constructed avenues for Soviet-era Russian immigrants and their descendants to join the Baltic ethnicities. In the reverse direction, Halpulaar'en consider those who have shifted to speaking Wolof to have left the ethnic group. (Note, though, that they are usually not then considered by the Wolof to have entered their ethnic group, creating a serious social problem.)

To continue the example of Zionist ideology, even secular Zionists consider converts to be Jews, and many consider converts to non-Jewish religions to have exited the tribe. Non-Jewish immigrants and their descendants who speak Hebrew as a native language may or may not be considered members depending on the person.