Context: 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.

Question: In modern secular usage Jews include how many groups?
Answer: three

Question: What makes the definition of a Jew vary slightly? 
Answer: whether a religious or national approach to identity is used

Question: Which religion shares some characteristics of a nation, an ethnicity, a religion and a culture?
Answer: Judaism

Question: What doesn't share any characteristics with a nation?
Answer: Unanswerable

Question: How many groups do Jews include in modern religious usage?
Answer: Unanswerable

Question: How many groups do Jews include in historical secular usage? 
Answer: Unanswerable

Question: Who is not included as a Jew in modern secular usage?
Answer: Unanswerable

Question: What has no effect on the definition of who is a Jew?
Answer: Unanswerable