CEA test: Carcinoembryonic antigen test is to detect response to therapy in cancer patients, especially colon cancer, with normal range of less than 2.5 (less than 5 in heavy smokers). Note that a positive test may not always be indicative of cancer.
Os Trigonum Syndrome. An Os Trigonum is a small, extra bone found at the back of the ankle in approximately 5-10% of people. Often it goes completely unnoticed, not causing any problems.
The trivia (singular trivium) are three lower Artes Liberales, i.e. grammar, logic and rhetoric. These were the topics of basic education, foundational to the quadrivia of higher education, and hence the material of basic education and an important building block for all undergraduates.