radiolucence
noun
ra·dio·lu·cence
¦rā-dē-ō¦lü-sᵊn(t)s
variants or radiolucency
¦rā-dē-ō¦lü-sᵊn(t)-sē 
plural radiolucences or radiolucencies
: the quality or state of being radiolucent
Word History
Etymology
radiolucence from radiolucent, after such pairs as English different : difference; radiolucency from radiolucent + -cy