| declining years(expression, idiom, age) |
| decomposition(decline, collapse, deterioration, impairment, degeneration) |
| decrease(noun, drop, decline, fall, collapse) |
| decrepit |
| deficiency(noun, disorder, weakness, fault, illness) |
| degeneracy(noun, drop, decline, fall, collapse) |
| degeneration(noun, drop, decline, fall, collapse) |
| delicate health |
| depreciation(decline, ruin, collapse, failing, deterioration) |
| devolution(noun, drop, fall, failure, deterioration) |
| diminution(noun, drop, fall, failure, deterioration) |
| diseasedness(noun, disorder, weakness, fault, illness) |
| disintegration(decline, collapse, deterioration, impairment, degeneration) |
| dissolution(noun, drop, decline, fall, collapse) |
| downfall(noun, drop, decline, fall, collapse) |
| downgrade(noun, drop, fall, failure, deterioration) |
| downturn(noun, drop, fall, failure, deterioration) |
| drop(noun, fall, failure, deterioration, falloff) |
| dwindling(noun, drop, decline, fall, failure) |
| dying(decline, ruin, collapse, failing, deterioration) |