What does Lena mean in Russian?

"Lena" itself is not a traditional Russian name, but it's commonly used as a shortened form of the Russian name Elena (Еле́на).

Elena is a Russian version of the Greek name Helen, meaning "light," "torch," or "bright one."

So, while "Lena" is not an independent Russian word with a specific meaning, it carries the same connotations of lightness, brightness, and radiance as the full name Elena.