CT

Ct is a compact abbreviation that can refer to several distinct concepts, depending on the context. In medical imaging, CT commonly stands for computed tomography, a diagnostic tool that uses rotating X-ray beams to create cross-sectional images of the body. CT data are reconstructed into two- or three-dimensional slices, enabling visualization of internal structures and the assessment of injuries, tumors, or other pathologies. CT scans may be enhanced with contrast agents to improve visibility of blood vessels and soft tissues. While highly informative, CT involves exposure to ionizing radiation, so its use is weighed against potential risks and cumulative dose.

In gemology and jewelry, ct denotes carat, a unit of mass used to quantify gemstone weight. One carat equals 200 milligrams, and a carat is subdivided into 100 points, allowing precise expressions such as 0.75 ct. Carat weight is a major factor in gemstone pricing and perceived size, though value also depends on cut, color, and clarity. It is distinct from karat, which measures gold purity rather than weight.

In timekeeping, CT is commonly used to denote Central Time, the time zone covering parts of the central United States, Canada, and Mexico. Central Time is UTC−6 during standard time and UTC−5 during daylight saving time, known as Central Daylight Time. The designation can vary by region and season, with some areas observing daylight saving changes and others remaining on a single standard offset.

The meaning of Ct or CT thus depends on domain and capitalization, underscoring the importance of context when interpreting the abbreviation.