I. adjective
1.
made up of two or more separable or identifiable elements
the complex vascular system of higher plants
Synonyms: composite, compound
Related Word: blended, compounded, mingled, mixed; heterogeneous, varied; elaborate, intricate, involved; complicated, confused, mixed-up
Contrasted words: homogeneous, uniform
Antonyms: simple
2.
difficult to comprehend because of a multiplicity of interrelated elements
a complex plot to undermine the government by discrediting its leaders
Synonyms: Byzantine, complicated, daedal, elaborate, gordian, intricate, involved, knotty, labyrinthine, sophisticated
Related Word: bewildering, confusing, distracting, disturbing; baffling, confounding, mysterious, mystifying, perplexing, puzzling; equivocal, obscure, vague; involute, involuted, reticular
Contrasted words: clear, defined, definite, distinct, plain, recognizable, uncomplicated, uninvolved; comprehensible, explicable, intelligible, knowable
Antonyms: simple
II. noun
Synonyms: system 1
Contrasted words: constituent, element, factor; member, part, piece, portion; detail, item, particular
Antonyms: component