Trans is a Latin word meaning "on the opposite side" and is the opposite of cis, which means "on the same side".

• In chemistry, a bond not subject to free rotation in which the greater radical on both ends is on the opposite side of the bond is called trans. Compare with cis.

In the diagram on the right, the hydrogen atoms are on opposite sides of the double bond. They cannot rotate to the same side of the molecule, as (unlike with a single bond) double bonds prevent this from happening.

See geometric isomerism for more on this topic. See also Trans fat

Trans is also:

• an airline, Trans World Airlines, or TWA.
• a commune in the Mayenne département, in France;
• commonly used as a short form of transsexual or transgendered, e.g. a transwoman, transman, transpeople. The term also serves as an umbrella term to include the entire trans community, although some (such as genderqueer and other gender variant people) do not use labels with the prefix;
• a 1982 album by Neil Young;
• not to be confused with trance.