This is the 4215th most frequent German word.
besonderem
"Besonderem" means "special" or "particular" (dative case of "besonderer").
Here, 'besondere' is an adjective in German used to describe 'Bedeutung' (meaning), denoting something distinct or not ordinary.
Dieses Bild hat eine besondere Bedeutung.
This picture has a special meaning.
In this sentence, 'besondere' acts as an adjective modifying 'Ereignisse' (events), illustrating uniqueness or significance pertaining to the friendship.
Unsere Freundschaft ist durch besondere Ereignisse geprägt.
Our friendship is shaped by special events.
In this case, 'Besonderem' is used as a dative adjective-derived noun referring to the emphasis or focus, showcasing nominalization of the adjective 'besonder'.