Originally Shmoneh Esreh only had 18 blessings, thus the name "Shemoneh Esreh." However, subsequently a 19th blessing was added of Velamalshinim regarding the heretics. If there are 19 blessings now, ...
The Siddur we use for Yom Tov is known as a Machzor. What does it mean and where did this originate?