Across; beyond; through.
[Latin trans, across.]
The key sense in this widely distributed form is that of being on the other side of something or moving across or straddling something. Modern examples relating to physical locations include transatlantic, transborder, and trans-Pacific; the area in Romania called Transylvania literally means ‘beyond the forest’ in Latin. Some examples, such as transalpine, situated in the area beyond the Alps (in particular as viewed from Italy), are often contrasted with forms in cis-.
Some examples imply a movement to another place, position, or situation: transmit (Latin mittere, send); transfer (Latin ferre, to bear); transpose (Latin poser, to place); transition (Latin transire, go across).
There can be an implication of change into another state or condition: transform (Latin formare, to form), translate (Latin translatus, carried across); transmute (Latin mutare, to change), change in form, nature, or substance; transsexual, a person having the physical characteristics of one sex but a strong and persistent desire to belong to the other.
Trans- can imply something surpassing: transcend (Latin scandere, climb), be or go beyond the range or limits of something;; transhistorical, going beyond historical boundaries, eternal; transfinite, in mathematics relating to or denoting a number corresponding to an infinite set.
Many words imported from Latin, or based on Latin elements, now have senses that are figurative: transact (Latin agere, do, lead), conduct or carry out business; transfix (Latin figere, fix, fasten), cause someone to become motionless with horror, wonder, or astonishment; transgress (Latin gradi, go), infringe some established standard of behaviour.
In some cases, the form became truncated to tra- or tre- in Latin, or in its passage from Latin into English: tradition (Latin dare, give), traverse (Latin vestire, clothe), trespass (Latin transpassare), traduce (Latin ducere, to lead).
In chemistry, trans- refers to a molecule in which two atoms or groups lie on opposite sides of a given plane in the molecule, as in trans-fatty acid, an unsaturated fatty acid with this arrangement of the carbon atoms next to its double bonds; other examples are transaminase, an enzyme; trans-2-butene; trans-1,2-dichlorocyclopentane; trans is often used as a word in its own right to refer to such arrangements. Its opposite is cis-.