Осенью я часто гуляю в парке.

In autumn I often walk in the park.

Breakdown of Осенью я часто гуляю в парке.

• я: I
• парк: the park
• в: in
• часто: often

Questions & Answers about Осенью я часто гуляю в парке.

Why is осенью used instead of осень?

Осенью is the instrumental case of the noun осень (autumn/fall).

For feminine nouns like осень, the instrumental singular ending is -ю:

• осень → осенью

Russian often uses the instrumental case (without a preposition) to say “in [a season]”:

• осенью – in (the) autumn
• зимой – in (the) winter
• весной – in (the) spring
• летом – in (the) summer

So осенью я часто гуляю в парке literally is “in-autumn I often walk in the park.”

Could I say в осени instead of осенью?

Not in normal, everyday Russian.

• осенью is the natural, standard way to say “in autumn / in the fall.”
• в осени is grammatically possible but sounds poetic, old-fashioned, or unusual, and is rarely used in modern speech.

So for everyday conversation, always use осенью.

Why is there no preposition like в or на before осенью, even though it means “in autumn”?