jew
'Judío' is a Spanish noun that translates to 'Jew' in English. It is used to refer to people who follow or are connected with Judaism, a monotheistic religion considered one of the world's major religious groups. This term is commonly used in Spanish-speaking countries to identify someone as a follower of Judaism, the same way 'Jew' is used in English.
He is a very devout Jew.
This sentence uses 'judío' to refer to someone who is a member of the Jewish faith. The adjective 'devoto' expresses that the person practices his religion with much dedication.
The Holocaust was a tragic event in Jewish history.
In this context, 'judío' is used as an adjective (Jewish) to describe the history to which the Holocaust belongs. Note that in Spanish, adjectives typically come after the noun they modify.
The synagogue is a meeting place for the Jewish community.
This sentence uses 'judía', the feminine form of 'judío' as an adjective to describe the community that meets in a synagogue. Again, the adjective placement is after the noun it is describing.