This is the 873rd most frequent Russian word.
бывшего
"Former" or "ex-"
In this sentence, 'бывшего' is used as an adjective describing 'сотрудника', meaning 'former'.
Я встретил бывшего сотрудника нашей компании.
I met a former employee of our company.
Here, 'бывшего' again functions as an adjective modifying 'гражданина', conveying the idea of something previous or past.
Мы часто говорим о правах бывшего гражданина этой страны.
We often talk about the rights of a former citizen of this country.
In this example, 'бывшего' describes 'правительства', showcasing its role as an adjective to indicate something that existed in the past.