1.  complex(n = noun.cognition) composite - a conceptual whole made up of complicated and related parts; "the complex of shopping malls, houses, and roads created a new town"

2.  complex(n = noun.substance) coordination compound - a compound described in terms of the central atom to which other atoms are bound or coordinated;

3.  complex(n = noun.feeling) - (psychoanalysis) a combination of emotions and impulses that have been rejected from awareness but still influence a person's behavior;

4.  complex(n = noun.artifact) building complex - a whole structure (as a building) made up of interconnected or related structures;

   complex(a = adj.all) - complicated in structure; consisting of interconnected parts; "a complex mass of diverse laws and customs"; "a complex set of variations based on a simple folk melody"
Antonym: simple
Derived form noun complexity₁, noun complexness₁

1.  Composed of two or more parts; composite; not simple; as, a complex being; a complex idea. [1913 Webster]

2.  Involving many parts; complicated; intricate. [1913 Webster]

   Assemblage of related things; collection; complication. [1913 Webster]

complex, n. & adj.
--n.
1 a building, a series of rooms, a network, etc. made up of related parts (the arts complex).
2 Psychol. a related group of usu. repressed feelings or thoughts which cause abnormal behaviour or mental states (see inferiority complex (see OEDIPUS COMPLEX)).
3 (in general use) a preoccupation or obsession (has a complex about punctuality).
4 Chem. a compound in which molecules or ions form coordinate bonds to a metal atom or ion.
--adj.
1 consisting of related parts; composite.
2 complicated (a complex problem).
3 Math. containing real and imaginary parts (cf. IMAGINARY).

Idiom:
complex sentence a sentence containing a subordinate clause or clauses.

Derivative:
complexity n. (pl. -ies). complexly adv.

Etymology:
F complexe or L complexus past part. of complectere embrace, assoc. with complexus plaited

N  whole, totality, integrity, totalness, entirety, ensemble, collectiveness, unity, completeness, indivisibility, indiscerptibility, integration, embodiment, integer, all, the whole, total, aggregate, one and all, gross amount, sum, sum total, tout ensemble, length and breadth of, Alpha and Omega, be all and end all, complex, complexus, lock stock and barrel, bulk, mass, lump, tissue, staple, body, compages, trunk, torso, bole, hull, hulk, skeleton greater part, major part, best part, principal part, main part, essential part, lion's share, Benjamin's mess, the long and the short, nearly, all, almost all, whole, total, integral, entire, complete, one, individual, unbroken, intact, uncut, undivided, unsevered, unclipped, uncropped, unshorn, seamless, undiminished, undemolished, undissolved, undestroyed, unbruised, indivisible, indissoluble, indissolvable, indiscerptible, wholesale, sweeping, comprehensive, wholly, altogether, totally, entirely, all, all in all, as a whole, wholesale, in a body, collectively, all put together, in the aggregate, in the lump, in the mass, in the gross, in the main, in the long run, en masse, as a body, on the whole, bodily, en bloc, in extenso, throughout, every inch, substantially, tout bien ou rien.

N  disorder, derangement, irregularity, anomaly, anarchy, anarchism, want of method, untidiness, disunion, discord, confusion, confusedness, mishmash, mix, disarray, jumble, huddle, litter, lumber, cahotage, farrago, mess, mash, muddle, muss, hash, hodgepodge, hotch-potch, hotch-pot, imbroglio, chaos, omnium gatherum, medley, mere mixture, fortuitous concourse of atoms, disjecta membra, rudis indigestaque moles, complexity, turmoil, ferment, to-do, trouble, pudder, pother, row, rumble, disturbance, hubbub, convulsion, tumult, uproar, revolution, riot, rumpus, stour, scramble, brawl, fracas, rhubarb, fight, free-for-all, row, ruction, rumpus, embroilment, melee, spill and pelt, rough and tumble, whirlwind, bear garden, Babel, Saturnalia, donnybrook, Donnybrook Fair, confusion worse confounded, most admired disorder, concordia discors, Bedlam, all hell broke loose, bull in a china shop, all the fat in the fire, diable a' quatre, Devil to pay, pretty kettle of fish, pretty piece of work, pretty piece of business, disorderly person, disorderly persons offence, misdemeanor, slattern, slut (libertine), disorderly, orderless, out of order, out of place, out of gear, irregular, desultory, anomalous, acephalous, deranged, aimless, disorganized, straggling, unmethodical, immethodical, unsymmetric, unsystematic, untidy, slovenly, dislocated, out of sorts, promiscuous, indiscriminate, chaotic, anarchical, unarranged &c (arrange), confused, deranged, topsy-turvy, shapeless, disjointed, out of joint, troublous, riotous, complex, irregularly, by fits, by fits and snatches, by fits and starts, pellmell, higgledy-piggledy, helter-skelter, harum-scarum, in a ferment, at sixes and sevens, at cross-purposes, upside down, the cart before the horse, hysteron proteron, chaos is come again, the wreck of matter and the crush of worlds.

N  complexity, complexness, complexus, complication, implication, intricacy, intrication, perplexity, network, labyrinth, wilderness, jungle, involution, raveling, entanglement, coil, sleave, tangled skein, knot, Gordian knot, wheels within wheels, kink, gnarl, knarl, webwork, difficulty, gnarled, knarled, complex, complexed, intricate, complicated, perplexed, involved, raveled, entangled, knotted, tangled, inextricable, irreducible.

N  number, symbol, numeral, figure, cipher, digit, integer, counter, round number, formula, function, series, sum, difference, complement, subtrahend, product, multiplicand, multiplier, multiplicator, coefficient, multiple, dividend, divisor, factor, quotient, submultiple, fraction, rational number, surd, irrational number, transcendental number, mixed number, complex number, complex conjugate, numerator, denominator, decimal, circulating decimal, repetend, common measure, aliquot part, prime number, prime, relative prime, prime factor, prime pair, reciprocal, totient, binary number, octal number, hexadecimal number, permutation, combination, variation, election, ratio, proportion, comparison, progression, arithmetical progression, geometrical progression, harmonical progression, percentage, permilage, figurate numbers, pyramidal numbers, polygonal numbers, power, root, exponent, index, logarithm, antilogarithm, modulus, base, differential, integral, fluxion, fluent, numeral, complementary, divisible, aliquot, reciprocal, prime, relatively prime, fractional, decimal, figurate, incommensurable, proportional, exponential, logarithmic, logometric, differential, fluxional, integral, totitive, positive, negative, rational, irrational, surd, radical, real, complex, imaginary, finite, infinite, impossible, numerically, modulo.