From Old Church Slavonic *lěto*, originally meaning simply "year" — a sense still preserved in words like *столетие* (century, lit. "a hundred years") and the plural *лет* (used in counting years: "ему 30 лет", "he is 30 years old"). The narrowing to "summer" happened in East Slavic while the "year" sense survived in compounds and formal registers. Cognate with Lithuanian *lėtas* (slow, calm) and possibly linked to Proto-Indo-European roots relating to light or warmth.

The Russian summer is brief but intensely celebrated — roughly June through August. It carries a strong cultural weight: the *dacha* (country cottage) culture revolves around лето, with city dwellers escaping to gardens and forests. The word also lives on in the Russian calendar idiom: *сколько тебе лет?* ("how old are you?" — literally "how many summers do you have?"), a charming echo of the archaic "year" meaning. June 21st is the summer solstice — the longest day of the year — making today a perfect day for this word.