A gradual decline (in size or strength or power or number).

synonyms: ebb, ebbing.

Roget 659: deterioration, debasement; wane, ebb; recession etc. 287; retrogradation etc. 283^†; decrease etc. 36.    degeneracy, degeneration, degenerateness; degradation; depravation, depravement; devolution; depravity etc. 945; demoralization, retrogression; masochism.    impairment, inquination^†, injury, damage, loss, detriment, delaceration^†, outrage, havoc, inroad, ravage, scath^†; perversion, prostitution, vitiation, discoloration, oxidation, pollution, defoedation^†, poisoning, venenation^†, leaven, contamination, canker, corruption, adulteration, alloy.    decline, declension, declination; decadence, decadency^†; falling off etc. v.; caducity^†, decrepitude.    decay, dilapidation, ravages of time, wear and tear; corrosion, erosion; moldiness, rottenness; moth and rust, dry rot, blight, marasmus^†, atrophy, collapse; disorganization; delabrement etc. (destruction). 162; aphid, Aphis, plant louse, puceron^†; vinefretter^†, vinegrub^†.    wreck, mere wreck, honeycomb, magni nominis umbra [Lat.]; jade, plug, rackabones [U.S.], skate [U.S.]; tackey^†, tacky [U.S.].    ... show more

Roget 36: decrease, diminution; lessening etc. v.; subtraction etc. 38; reduction, abatement, declension; shrinking etc. (contraction.) 195; coarctation^†; abridgment etc. (shortening) 201; extenuation.    subsidence, wane, ebb, decline; ebbing; descent etc. 306; decrement, reflux, depreciation; deterioration etc. 659; anticlimax; mitigation etc. (moderation) 174.    ... show more

Grow smaller:
— Interest in the project waned.

synonyms: decline, go down.

Roget 36: decrease, diminish, lessen; abridge etc. (shorten) 201; shrink etc. (contract) 195; drop off, fall off, tail off; fall away, waste, wear; wane, ebb, decline; descend etc. 306; subside; melt away, die away; retire into the shade, hide its diminished head, fall to a low ebb, run low, languish, decay, crumble.    bate, abate, dequantitate^†; discount; depreciate; extenuate, lower, weaken, attenuate, fritter away; mitigate etc. (moderate) 174; dwarf, throw into the shade; reduce etc. 195; shorten etc. 201; subtract etc. 38.    ... show more

Roget 128: be aged etc. adj.; grow old, get old etc. adj.; age; decline, wane, dodder; senesce.   

Roget 195: become small, become smaller; lessen, decrease etc. 36; grow less, dwindle, shrink, contract, narrow, shrivel, collapse, wither, lose flesh, wizen, fall away, waste, wane, ebb; decay etc. (deteriorate) 659.    be smaller than, fall short of; not come up to etc. (be inferior) 34.    render smaller, lessen, diminish, contract, draw in, narrow, coarctate^†; boil down; constrict, constringe^†; condense, compress, squeeze, corrugate, crimp, crunch, crush, crumple up, warp, purse up, pack, squeeze, stow; pinch, tighten, strangle; cramp; dwarf, bedwarf^†; shorten etc. 201; circumscribe etc. 229; restrain etc. 751.    [reduce in size by abrasion or paring. ] (subtraction) 38 abrade, pare, reduce, attenuate, rub down, scrape, file, file down, grind, grind down, chip, shave, shear, wear down.    ... show more

Dutch: slinken

Become smaller.

Decrease in phase.