This is the 10580th most frequent Russian word.
внезапные
Sudden.
The word 'внезапные' in this context modifies 'changes' (изменения), emphasizing their abrupt nature.
Внезапные изменения в планах удивили всех.
Sudden changes in plans surprised everyone.
The word 'внезапным' in this sentence describes 'visits' (визитам), indicating they occur unexpectedly.
Он был готов к внезапным визитам гостей.
He was prepared for sudden visits from guests.
Here, 'внезапное' describes 'insight' (озарение), indicating its unexpected occurrence.