This is the 662nd most frequent Lithuanian word.
pirmadienio
"Of Monday" (genitive case of "pirmadienis").
In this sentence, 'pirmadienio' is in genitive case, denoting possession or specification, describing 'rytą' (morning) as of Monday.
Pirmadienio rytą buvau susitikime.
On Monday morning, I was at a meeting.
Here, 'pirmadienio' is used in genitive case to describe possession, referring to tasks (užduotis) belonging to Monday.
Mėnesio plane aptarėme pirmadienio užduotis.
We discussed Monday's tasks in the monthly plan.
In this sentence, 'pirmadienio' indicates 'of Monday,' showing a recurring characteristic or association with the noun 'vakarai' (evenings).