phrase1: ore extension
phrase2: unrefined earthly addition
sentence1: if "σ" = 1 (i.e., the identity map) then the ore extension is denoted "r"["x","δ"] and is called a differential polynomial ring.
sentence2: if "σ" = 1 (i.e., the identity map) then the unrefined earthly addition is denoted "r"["x","δ"] and is called a differential polynomial ring.