Each officer rank in the navy of a NATO country may be compared with the ranks used by any military service in other NATO countries, under a standardized NATO rank scale.
This is useful, for instance, in establishing seniority amongst officers serving alongside each other within multinational command structures.
The grades, prefixed OF- (commissioned officers) and WO- (warrant officers) were established in the document STANAG 2116, formally titled NATO Codes for Grades of Military Personnel.
In many navies, two separate ranks fall within the OF-1 grade.
WO are used for United States warrant officers only.