IPA: /dɪˈsɛnɪəli/
KK: /dɪˈsɛnɪəli/
This word describes something that happens every ten years.
The festival is celebrated decennially, attracting visitors from all over the world.
Decennially is formed from "decennium" (from Latin, meaning ten years) and the suffix "-ally" (meaning in a manner relating to). The word refers to something that occurs every ten years.
Think of a period of 'ten years' ('decennium') and how the suffix '-ally' indicates a manner of occurrence. This helps you remember that 'decennially' means something that happens every ten years.