This is the 132nd most frequent Ukrainian word.
січня
"Січня" is the genitive form of "січень," which means "January" in English.
Here 'січні' is used to indicate the time period of January.
У січні ми відпочивали в горах.
In January, we vacationed in the mountains.
Here 'січня' is used to denote a specific date. It is in the genitive case as part of a date expression.
Першого січня я почав нову книгу.
On the first of January, I started a new book.
Here 'січня' is used to specify the starting point in time. It appears in the genitive case after the preposition 'від'.