A radical is a molecule with an odd number of electrons, and is induced in a variety of ways, including ultra-violet radiation. A sun burn is largely due to radical formation from this radiation. The radical-pair, however, is not simply two radicals.
A radical has an odd number of electrons and can be induced by various methods, like ultra-violet light. Sunburns are primarily due to the formation of these radicals. In contrast, a radical pair is not simply two radicals.