A piyyut or piyut (plural piyyutim or piyutim, Hebrew: פִּיּוּטִים / פיוטים, פִּיּוּט / פיוט pronounced [piˈjut, pijuˈtim]; from Greek ποιητής poiētḗs "poet") is a Jewish liturgical poem, usually designated to be sung, chanted, or recited during religious services. Piyyutim have been written since Temple times. Most piyyutim are in Hebrew or Aramaic, and most follow some poetic scheme, such as an acrostic following the order of the Hebrew alphabet or spelling out the name of the author. Many piyyutim are familiar to regular attendees of synagogue services. For example, the best-known piyyut may be Adon Olam ("Master of the World"). Its poetic form consists of a repeated rhythmic pattern of short-long-long-long (the so-called hazaj meter), and it is so beloved that it is often sung at the conclusion of many synagogue services, after the ritual nightly recitation of the Shema, and during the morning ritual of putting on tefillin phylacteries. Another beloved piyyut is Yigdal ("May God be Hallowed"), which is based upon the Thirteen Principles of Faith set forth by Maimonides. Important scholars of piyyut today include Shulamit Elizur and Joseph Yahalom, both at Hebrew University. The author of a piyyut is known as a paytan, payetan or payyetan (פייטן); plural paytanim (פייטנים). Source: Wikipedia (en)