THESAURUS
sector
adjunct, component, contingent, crescent, cross section, detachment, detail, district, division, dole, fraction, half circle, hemicycle, installment, item, parcel, part, particular, percentage, portion, precinct, quadrant, quarter, quota, random sample, remainder, sample, sampling, section, segment, semicircle, sextant, share, subdivision, subgroup, subspecies
ROGET THESAURUS
sector
Part
N
part, portion, dose, item, particular, aught, any, division, ward, subdivision, section, chapter, clause, count, paragraph, verse, article, passage,
sector, segment, fraction, fragment, cantle, frustum, detachment, parcel, piece, lump, bit cut, cutting, chip, chunk, collop, slice, scale, lamina, small part, morsel, particle, installment, dividend, share, debris, odds and ends, oddments, detritus, excerpta, member, limb, lobe, lobule, arm, wing, scion, branch, bough, joint, link, offshoot, ramification, twig, bush, spray, sprig, runner, leaf, leaflet, stump, component part, sarmentum, compartment, department, county, fractional, fragmentary, sectional, aliquot, divided, in compartments, multifid, disconnected, partial, partly, in part, partially, piecemeal, part by part, by by installments, by snatches, by inches, by driblets, bit by bit, inch by inch, foot by foot, drop by drop, in detail, in lots.
Circularity
N
circularity, roundness, rotundity, circle, circlet, ring, areola, hoop, roundlet, annulus, annulet, bracelet, armlet, ringlet, eye, loop, wheel, cycle, orb, orbit, rundle, zone, belt, cordon, band, contrate wheel, crown wheel, hub, nave, sash, girdle, cestus, cincture, baldric, fillet, fascia, wreath, garland, crown, corona, coronet, chaplet, snood, necklace, collar, noose, lasso, lassoo, ellipse, oval, ovule, ellipsoid, cycloid, epicycloid, epicycle, semicircle, quadrant, sextant,
sector, sphere, round, rounded, circular, annular, orbicular, oval, ovate, elliptic, elliptical, egg-shaped, pear-shaped, cycloidal, spherical, I watched the little circles die.