diminution-n; 2 Senses

Sense Number 1: the reduction of the extent of something, e.g, its size, importance or quantity

Commentary: DIMINUTION[+action][+reduction][+extent][+size/+importance/+quantity]

Their economic policies have led to a diminution of their currency.
The epidemic of influenza shows no signs of diminution.
Political satire uses diminution of character as a device.

WordNet 3.0 Sense Numbers: 1, 3

Sense Number 2: a variant of a musical theme which employs notes of reduced duration from the original theme

Commentary: DIMINUTION[+entity][+symbolic][+form][+musical][+theme][+reduced][+duration][+note]

There are many effective diminutions in Pachelbel's Canon in D.
John wrote an eighth note diminution to his quarter note motif in C minor.

WordNet 3.0 Sense Numbers: 2