This is the 17780th most frequent Russian word.
уменьшаться
"To decrease" or "to diminish."
The word 'уменьшаться' is used here to describe the process of a physical quantity, the volume of water, reducing in size or amount.
Объем воды в реке начал уменьшаться из-за засухи.
The volume of water in the river began to decrease due to the drought.
The word 'уменьшаться' is utilized in this sentence to convey the reduction of an abstract numerical measure, percentage, over time.
Процент satisfied клиентов стал уменьшаться после введения новых правил.
The percentage of satisfied customers began to reduce after the implementation of new rules.
Here, 'уменьшаться' figuratively indicates a lessening or decline in the emotional state or mood of individuals.