jǐ​shí

several tens

几十 (幾十) jǐ​shí
several tens numeral
a number greater than twenty but less than one hundred, often used to indicate an indefinite large amount.

He has worked here for several decades.

Frequency

Movie subtitles
5.63 per million appears in 3% of films
Written text
44.2 per million

Sources

Definitions
AI-generated definitions