sena

1. formal shadow; shade
   Sedeli su u seni starog oraha. — They sat in the shade of an old walnut tree.
2. formal ghost; shade; spirit
   Palili su sveće za sene predaka. — They lit candles for the spirits of their ancestors.
3. (plant) senna
   Čaj od sene pomaže kod zatvora. — Senna tea helps with constipation.

In everyday speech senka is normally used instead of sena.