Curvature is defined as a lens inability to be flat, or the degree to which a lens curves. Now, lets think about this. A lens curvature represents a part of a circle. If you increase the curvature, in other words, curve the lense more, that would make the circle smaller. A radius is the distance from the center of the circle to the outside of the circle. So if you effectively make the circle smaller, you also decrease the radius of the circle. This is sort of tricky, what is known as an inverse or indirect relationship. If we increase the amount of curvature, we get a decrease in the amount of curvature radius. Or, we could go the other way, if we decrease the amount of curvature, we get an increase in the amount of curvature radius. In any event, when one factor moves, the other factor goes in an opposite direction. So, the bottom line is, increasing the curvature of the lens would decrease the radius of curvature.
If the curvature of a lens is more then its radius will be less. This is because when we take a small sphere/circle, its circumference is more curved as a complete rotation should be taken with less distance. this increases the curvature. Thus a less curved lens has moreradiusof curvature.
Note:A plain glass has the no curvature as its radius of curvature is infinite ie greater thean any real number.