definition
strict definition
secondary country division tier
The second level of subdivision inside a country, below the first and above the municipality.
The secondary country division tier holds the level below the first: the county, the district, the arrondissement, the raion, the Landkreis. It groups municipalities and answers to the division above it.
Not every country has this level. Where municipalities sit directly under the first-level division, the tier is empty for that country, and a record must not invent a unit to fill it.
What the unit is called is the region type. The tier says only that one level of subdivision lies above it and the municipalities lie below.