These words refer to a lessening in numbers, intensity or volume. Decrease and dwindle can both be applied widely but are particularly pertinent to a reduction in numbers. Of the two, decrease is the more general and has fewer connotations.

• In winter, the number of arrests generally decrease ; The number of nations allied with us decreased as the war continued.

Where decrease can apply as well to a reduction in undesirable things, dwindle usually suggests a loss of something valuable; the word often gives a lyrical or elegiac tone and can suggest a wasting process.

• Sanctuaries for wildlife have dwindled alarmingly in the last decade; His health dwindled slowly day by day.

Abate and subside both point to a slow reduction in intensity: The ferocity of the enemy’s counter attack abated after the first few hours. Subside can in particular suggest a return to clam or repose after agitation: a violent struggle after which he subsided into a feverish sleep. Like one possibility for dwindle , both these words are often applied to a slow loss of strength or health.

Decline and sink are particularly relevant to a reduction in volume. Decline is more neutral and factual, whereas sink can give a lyrical or elegiac tone. While both can apply to illness, both also can refer factually to the gradual reduction in the measurable level of something: The volume of shares traded declined as prices continued to sink throughout the day. Both refer metaphorically to a downward trend, but sink is more graphic here can suggest a more drastic or quicker movement: daylight that declined almost infinitesimally at first and then sank away rapidly when the sun had set. Sink is relatively-informal when compared to the previous words.

Drop and fall both concentrate on a sudden downward movement or a reduction in numbers, intensity or volume. Both, like sink , are relatively informal. A possible distinction between the two exists in that drop might more naturally describe reduction and fall an unfortunate eradication programme; The standard of debate fell to a new low, with name-calling and denunciation replacing rational discourse.

When fall in used with off, the word applies more generally to any decline, slow or rapid, good or bad: Unemployment continued to fall off in the third quarter.