What relationship is there when a R-Squared (coefficient of determination) value=0.51?

Question

When running a linear regression between Degree of Urbanization and the Ranking of a country on the Human Development Index the result is that there is a "__________?????" relationship (R-squared = 0.51). This means that 49% of the variance of Human Development Index Ranking is not explained by the variance in the Degree of Urbanization. Meaning that being highly urbanized doesn’t necessary relate to or mean that a country will Rank higher on the Human Development Index.

Can someone please verify my logic behind my statistical claim and identify the meaning of R²=0.51? I want to fill in that blank.

Answer 1

Back in Math 1 we'd have called that a weak positive correlation.