The word "Siddur" refers to a Jewish prayer book that contains daily prayers and blessings. There are various terms that are used synonymously with Siddur in different Jewish traditions. In Orthodox Judaism, the word "Machzor" is used for the prayer books used during festivals and High Holy Days. The term "Nusach" is used to indicate the specific version or style of prayer service that is followed by various communities. In Sephardic and Mizrahi traditions, the word "Tefillah" is often used instead of Siddur. Additionally, in Reform and Conservative Judaism, the terms "Prayer Book" or "Service Book" are frequently used instead of Siddur. Despite the different names, all these books serve the same purpose of providing a structured approach to Jewish prayer.