This is the 3374th most frequent Polish word.
wspólnym
"Shared" or "common."
The word 'wspólnym' describes the nature of the dinner, indicating that it is shared or organized jointly.
Spotkaliśmy się na wspólnym obiedzie.
We met for a joint dinner.
Here, 'wspólnym' specifies that the project is a collaborative effort or shared responsibility.
Podjęliśmy decyzję o wspólnym projekcie.
We made a decision about a joint project.
In this sentence, 'wspólnych' indicates features or interests that are shared or mutual.