From Proto-Slavic *lěsъ, meaning "forest, woodland." Cognates appear across Slavic languages: Polish *las*, Ukrainian *ліс (lis)*, Czech *les*. The root may be connected to Proto-Indo-European *leh₂ys- ("brushwood, thicket"). The word has been central to Russian life and literature for centuries, given that forest covered much of the historical East Slavic homeland.

The forest (*лес*) holds an iconic place in Russian culture and folklore. It is the dwelling of mythological figures such as Baba Yaga (Баба-яга), the witch who lives in a hut deep in the woods. Expressions like *заблудиться в трёх соснах* ("to get lost among three pine trees," meaning to be confused by something simple) reflect how deeply the forest is woven into the Russian imagination. Russia is home to the world's largest boreal forest (taiga), so *лес* is both a daily word and a cultural symbol.