Летом мы покупаем черешню, а осенью — тыкву.

we

Breakdown of Летом мы покупаем черешню, а осенью — тыкву.

• покупать: to buy
• а: and
• летом: in summer

Questions & Answers about Летом мы покупаем черешню, а осенью — тыкву.

Why are летом and осенью not in their dictionary forms лето and осень?

Because here they are being used as time expressions, and Russian normally puts season words in the instrumental case in this pattern:

• лето → летом
• осень → осенью

This instrumental form often means in summer, in autumn, etc.

You will see the same with other seasons:

• зима → зимой
• весна → весной

So летом and осенью are very natural adverb-like forms meaning during summer and during autumn.

Why is there no preposition before летом and осенью? In English we say in summer and in autumn.

Russian often does not use a preposition with seasons in this kind of general time expression. The instrumental case alone carries that meaning.

So Russian says:

• летом = in summer
• осенью = in autumn
• зимой = in winter
• весной = in spring

This is one of those places where Russian is more compact than English.