Questions & Answers about Pod łóżkiem leżą czyste skarpetki.
Because pod can take different cases, and here it describes location: under the bed.
When pod means where?, Polish uses the instrumental case:
- pod łóżkiem = under the bed
The noun łóżko changes in the instrumental singular to łóżkiem.
Compare:
- Pod łóżkiem leżą skarpetki. = The socks are under the bed. → location
- Wkładam skarpetki pod łóżko. = I put the socks under the bed. → movement toward a place, so accusative
So a useful rule is:
- pod + instrumental = location
- pod + accusative = motion/direction