This is the 159th most frequent Swedish word.
januari
January.
Here, 'januari' is used as a proper noun to specify the first month of the calendar year.
Januari är den första månaden på året.
January is the first month of the year.
In this sentence, 'januari' is used as the time period to indicate when the vacation will occur.
Vi planerar att åka på semester i januari.
We plan to go on vacation in January.
Here, 'januari' is used as a descriptor of time, referring to a conceptual quality (coldness) occurring during this month.