How many letters does the top answer for “an anniversary of the day on which a person was born (or the celebration of it)” have?

The most common answer is birthday (8 letters).

Crossword clue: an anniversary of the day on which a person was born (or the celebration of it)

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

birthday 8 letters wn-def

an anniversary of the day on which a person was born (or the celebration of it)