Term 	Definition 
Always	"Denotes that property value or relationship applies at all observed locations, and is expected to apply everywhere."
Common	"Denotes that property value or relationship applies at most observed locations, and is expected to apply at most locations."
Sometimes	"Denotes that property value or relationship is observed at less than 25 percent of  locations, and is expected to apply at less than a quarter of locations."
Rare	"Denotes that property value or relationship is observed at less than 1 percent of  locations, and is expected to apply only rarely."
Never	"Denotes that property value or relationship has not been observed, and is not expected to apply at any location or under any condition."