Летом мы любим играть в волейбол на пляже.

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Breakdown of Летом мы любим играть в волейбол на пляже.

• на: on
• мы: we
• играть: to play

Questions & Answers about Летом мы любим играть в волейбол на пляже.

Why is летом used without a preposition? I expected something like в лето or в летом for in summer.

In Russian, names of seasons are very often used in the instrumental case with no preposition to mean during that season.

So:

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

This is a very common time expression pattern.

• Летом мы любим играть... = In summer, we like to play...

Notes:

• в летом is incorrect.
• в лето is not the normal way to say in summer in this meaning.

So летом is best understood as a fixed, very common adverb-like time expression.

What case is летом, and why?

Летом is the instrumental singular form of лето.

Here, the instrumental is used in a special adverbial way to express time when something happens, especially with seasons and some other time words.

Base noun:

• лето = summer

Instrumental singular:

• летом

So grammatically, it is still a noun form, but in practice it functions a lot like an adverb: in summer / during the summer.