Even without subtraction defined, N is useful. Partial subtraction on N, as it is, is also useful. When I'm dealing with counts I pretty explicitly either want

Even without subtraction defined, N is useful. Partial subtraction on N, as it is, is also useful. When I'm dealing with counts I pretty explicitly either want truncated subtraction or warnings when I overflow. Perhaps the biggest issue all together is just that many languages will let you do 3u - 4u instead of outright making the syntax more obviously annoying to force you to think about the caveats and pick between {truncated, throwing, overflow} variants.