This is the 9163rd most frequent Russian word.
сергей
"Сергей" is a Russian male given name, equivalent to "Sergey" or "Serge" in English.
Here, 'Сергей' is used as a proper noun referring to a person's name.
Меня зовут Сергей.
My name is Sergei.
Here, 'Сергей' is used as the object in the clause, representing the individual being observed.
Я видел, как Сергей играл в футбол.
I saw Sergei playing football.
In this sentence, 'Сергей' is the subject indicating the person performing the action.