1. What term refers to people who share a common language, customs, or heritage?

2. What term refers to people who share common ideological, philosophical, or theistic beliefs?

3. Which of these would be an ethnic group?

The terms to refer both to people who share common language, customs or heritage and to people who share common ideological, philosophical, or theistic beliefs is ehtnic group. This is the answer to questions 1 and 2 is ethnic group. Think that ethnicity refers to the indetification of people based on social experience or ancestry. Then, of course the answer to the third question is that both are ethnic groups.