What is "nusach"

Nusach ( nosaħ, modern pronunciation nósakh or núsakh), plural nuschaot or nusachim, is a concept in Judaism that has two distinct meanings. One is the style of a prayer service ( Nosach Teiman, Nusach Ashkenaz, Nusach Sefard or Nusach Ari); another is the melody of the service depending on when the service is being conducted.