Learner's definition of CELEBRATION
a party or other special event that you have for an important occasion, holiday, etc.
the activity of doing special, enjoyable things for an important occasion, achievement, etc.
the activity of celebrating
It was a night of celebration.
We're having a dinner in celebration of their anniversary. [=as a way of celebrating their anniversary]
Your promotion is (a) cause for celebration.
the performance of a religious ceremony
— usually singular