Complex sentence: Chinese Martyrs is a term which usually refers to individuals named specifically by both the Roman Catholic Church and the Eastern Orthodox Church who were killed in China during the 19th and early 20th centuries; they are celebrated as martyrs by their respective churches.
Split into simpler sentences: Chinese Martyrs is the name given to a number of Christians who died in China during the 19th and early 20th centuries. Named specifically by both the Roman Catholic Church and the Eastern Orthodox Church, they are celebrated as martyrs by their respective churches.