Trienial or Triennial: How To spell?

The word Trienial is misspelled against Triennial, meaning "Taking place every third year."

Triennial has double "nn" is mispronounced as "n"
Remember double 'NN' in between the strings trie & ial which should not be misspelled with single 'N'
Wrong Spelling: trie-n-ial
Correct Spelling: trie-nn-ial
Find more wrongly spelled words of Triennial to spell it well.