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.
Trigonometric parallax is the apparent displacement of a nearby star against the background of more distant stars resulting from the motion of the earth in its orbit around the sun. Formally, the parallax of a star is the angle at the star that is subtended by the mean distance between the earth and the sun.