Diminution (noun)

1. The reduction or decrease of something, especially in size, amount, or value.
2. The process or fact of becoming smaller or less.

Origin:

Middle english: from old french, from latin diminutio(n-), from the verb diminuere "lessen".

Examples:

1. The diminution of the population of endangered species is a major concern for wildlife conservation.
2. The diminution of ozone layer is harmful to human health.
3. The company has experienced a significant diminution in profits over the past year.
4. There has been a marked diminution in the size of the glacier due to global warming.
5. The diminution of pain was a result of the medicine he took.