1.  decrement(n = noun.attribute) decrease - the amount by which something decreases;
is a kind of amount
has particulars: dip, drop, fall, free fall, shrinkage

2.  decrement(n = noun.process) decrease - a process of becoming smaller or shorter;
is a kind of physical process, process
has particulars: decay, decline, decline, diminution, desensitisation, desensitization, narrowing, slippage, wastage
Antonym: increment

decrement, n.
1 Physics the ratio of the amplitudes in successive cycles of a damped oscillation.
2 the amount lost by diminution or waste.
3 the act of decreasing.

Etymology:
L decrementum (as DECREASE)

N  nonincrease, decrease, decrease, diminution, lessening, subtraction, reduction, abatement, declension, shrinking (contraction, ), coarctation, abridgment, extenuation, subsidence, wane, ebb, decline, ebbing, descent, decrement, reflux, depreciation, deterioration, anticlimax, mitigation, unincreased, decreased, decreasing, on the wane, a gilded halo hovering round decay, fine by degrees and beautifully less.

N  decrement, discount, defect, loss, deduction, afterglow, eduction, waste.

N  contraction, reduction, diminution, decrease of size, defalcation, decrement, lessening, shrinking, compaction, tabes, collapse, emaciation, attenuation, tabefaction, consumption, marasmus, atrophy, systole, neck, hourglass, condensation, compression, compactness, compendium, squeezing, strangulation, corrugation, astringency, astringents, sclerotics, contractility, compressibility, coarctation, inferiority in size, contracting, astringent, shrunk, contracted, strangulated, tabid, wizened, stunted, waning, neap, compact, unexpanded &c (expand), contractile, compressible, smaller &c (small).