Orthodox

Orthodox is a word about beliefs. It is made from two Ancient Greek words, ὀρθός orthós „correct, straight“ and δόξα dóxa „teaching, worship".   Orthodoxy means a teaching that is supposed to be close to the original. 

In particular:

in Christianity:

 Eastern Orthodox Church (The split of the Christian Church into the Roman Catholic Church and the Eastern Orthodox happened in 1054, in what is known as the Great Schism)
 Oriental Orthodox Church (Split from the rest in the 5th century, at the Council of Chalcedon)
 Theologically traditional often in all lower case-- orthodox

in Judaism:
 Orthodox Judaism
 Modern Orthodox Judaism

Jewish organisations:
 Orthodox Union