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.
Who is not included as a Jew in modern secular usage?