This is the 1485th most frequent Polish word.
księżyca
The Polish word "księżyca" means "of the moon" (genitive case of "księżyc").
The usage of 'księżyca' here is in the genitive case, used to indicate possession or relation, linked to the noun 'blask' which means 'glow'.
Blask księżyca odbija się na powierzchni rzeki.
The glow of the moon reflects on the surface of the river.
In this sentence, 'księżyca' is in the genitive case, describing the noun 'pełni', which means 'fullness' (of the moon).
Podczas pełni księżyca niebo jest wyjątkowo jasne.
During the full moon, the sky is exceptionally bright.
Here, 'księżyca' is in the genitive case as it is connected with the noun 'kształt', meaning 'shape', to imply a relationship of form.