Dictionary.com's Word of the Year is...
1650s, "composed of parts," from French complexe "complicated, complex, intricate" (17c.), from Latin complexus "surrounding, encompassing," past participle of complecti "to encircle, embrace," in transferred use, "to hold fast, master, comprehend," from com- "with" (see com-) + plectere "to weave, braid, twine, entwine," from PIE *plek-to-, from root *plek- "to plait" (see ply (v.1)). The meaning "not easily analyzed" is first recorded 1715. Complex sentence is attested from 1881.
1650s, "a whole comprised of parts," from complex (adj.). Psychological sense of "connected group of repressed ideas" was established by C.G. Jung, 1907.
complex com·plex (kŏm'plěks')
A group of related, often repressed memories, thoughts, and impulses that compel characteristic or habitual patterns of feelings, thought, and behavior.
The relatively stable combination of two or more ions or compounds into a larger structure without covalent binding.
A composite of chemical or immunological structures.
An entity made up of three or more interrelated components.
A group of individual structures known or believed to be anatomically, embryologically, or physiologically related.
The combination of factors, symptoms, or signs that forms a syndrome.
Consisting of interconnected or interwoven parts; composite.
Composed of two or more units.
Relating to a group of individual structures known or considered to be anatomically, embryologically, or physiologically related.
in chemistry, a substance, either an ion or an electrically neutral molecule, formed by the union of simpler substances (as compounds or ions) and held together by forces that are chemical (i.e., dependent on specific properties of particular atomic structures) rather than physical. The formation of complexes has a strong effect on the behaviour of solutions. See also chemical association; coordination compound.