What does tricyclic mean?
Tricyclic is chiefly a technical adjective describing an organic compound whose molecular structure contains three fused rings. In chemistry, the word identifies a structural arrangement and is often used with terms such as “compound,” “ring system,” and “molecule.” In pharmacology, tricyclic is especially associated with tricyclic antidepressants, a group of medicines used primarily in the treatment of depression, although some are also used for other conditions. As a noun, “a tricyclic” can refer to such a drug, but the full expression is more precise and more common in formal writing. The word is not a general synonym for three-ringed: its reference is specifically to a molecular structure. Its formation is transparent, combining tri-, meaning three, with cyclic, meaning circle-related, and it remains most familiar in scientific and medical contexts.
Having a molecular structure composed of three fused rings; relating to such structures or compounds.
"The synthetic route produced a stable tricyclic ring system."
This is the principal technical and adjectival use of the word.
Relating to or denoting tricyclic antidepressant drugs.
"The medication had tricyclic properties that required caution."
This sense is usually encountered in the established phrase “tricyclic antidepressant.”
A compound or drug whose molecular structure has three fused rings, especially a tricyclic antidepressant.
"Several tricyclics remain effective options when other antidepressants are unsuitable."
The standalone noun is less common and less specific than the phrase “tricyclic antidepressant.”
The plural is used when referring collectively to tricyclic drugs, especially tricyclic antidepressants.
"The review compared several tricyclics with newer antidepressant medications."
The name is a molecular blueprint: tri- means three, and cyclic means arranged in rings.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does tricyclic come from?
Tricyclic combines the combining form tri-, from Greek for “three,” with cyclic, which derives from Greek kyklikos, meaning “pertaining to a circle” or “circle-related.” The resulting word literally describes a cyclic arrangement in threes. It belongs to the same broad family as cyclic, bicyclic, monocyclic, and polycyclic, terms developed for compounds with differing numbers of rings.
Related word forms
How tricyclic is actually used
The word is chiefly used in chemistry, pharmacology, and related technical writing. Its standalone use as a noun is less formal than the fuller phrase “tricyclic antidepressant,” and it should not be used merely to mean any object arranged in three rings.
Easily confused with tricyclic
A tricyclic compound has three fused rings, whereas a bicyclic compound has two.
A tricycle is a three-wheeled vehicle, while tricyclic describes a three-ring molecular structure or a related compound.