This is the 15411th most frequent Russian word.
праздничного
"Festive" or "holiday-related".
The word "праздничного" is the genitive form of "праздничный," describing the type of cake purchased, indicating that it is suitable for a celebration.
Мы купили праздничного торта на вечеринку.
We bought a celebratory cake for the party.
The word "праздничного" is part of a possessive phrase referencing the festive attire, showing the specific association with celebration.
Она наденет своё праздничного платье завтра.
She will wear her festive dress tomorrow.
The word "праздничного" here is used to describe the drink being made, emphasizing its festive nature.