"Radiolucent" refers to materials that allow the passage of X-rays or other forms of radiation. In medical imaging, such as X-rays or CT scans, radiolucent substances appear dark on the images because they do not absorb much radiation. This property is useful for identifying structures within the body, such as organs or tissues. Common examples of radiolucent materials include air and certain types of plastic. In contrast, radiopaque materials, like bone or metal, block radiation and appear white on imaging. Understanding the difference between these two properties is essential for accurate diagnosis and treatment planning in medical settings.