Azymes is an archaic English word for the Jewish matzah, a word of ancient origin derived from the Greek word "ἄζυμος" (ázymos - "unleavened"). Azymes refers to unleavened bread in liturgical use by Western Christians.
While cognates of the Greek term are still used in many Romance languages: (Spanish: pan ácimo, French: pain azyme, Italian: azzimo, Romanian: azimă), the term does not appear frequently in modern Bible translations. It was the usual word for unleavened bread in the early Roman Catholic English Douay-Rheims Bible. The Church of Rome began the use of unleavened bread, the Azymes, during the latter part of the first millennium.
The Orthodox Church has continued the ancient practice of using leavened bread (Artos) for the Lamb (Host) in the Eucharist. When the Western Church began to use unleavened bread, azymes, for the Eucharist, this became a point of liturgical and theological difference between the Eastern and Western Churches and was one of issues that led eventually to the Great Schism between Eastern and Western Christianity in 1054.