Key

An NSNumber containing the numeric quantity represented by the localized substring.

A string containing an abbreviation that can be substituted for the substring when there is not enough room to display the original substring.

A number indicating the priority for which the substring should be substituted with the abbreviation specified by the NSAttributedString.Key.abbreviation key.

A substring with a lower abbreviation priority value should be abbreviated before a substring with a higher abbreviation priority value.