This is the 9807th most frequent Russian word.
ян
"Ян" is a Russian male given name, equivalent to "Jan" or "John" in English.
Here, 'Yan' is used as a proper noun, which is a male given name.
Ян пришёл домой и открыл книгу.
Yan came home and opened a book.
In this sentence, 'Jan' refers to a month abbreviation and signifies the month of January.
В календаре отмечен Ян на первом месте.
In the calendar, Jan is marked in the first place.
Again, 'Yan' serves as a proper noun referring to a person's given name.