Is jewish an ethnicity?

[Wizened wizard]

This is from Wikipedia: "Who is a Jew? Judaism shares some of the characteristics of a nation, an ethnicity, a religion, and a culture, making the definition of who is a Jew vary slightly depending on whether a religious or national approach to identity is used. Generally, in modern secular usage, Jews include three groups: people who were born to a Jewish family regardless of whether or not they follow the religion; those who have some Jewish ancestral background or lineage (sometimes including those who do not have strictly matrilineal descent); and people without any Jewish ancestral background or lineage who have formally converted to Judaism and therefore are followers of the religion."