How to spell millennium
millennium
Not millenium or milennium.
The trap
The spelling millennium has two Ls and two Ns, and millenium is the version that drops an N. The double L is easy to see; the double N goes because a doubled N sounds exactly like a single one.
Doubled letters are part of how a word is built, not decoration. The reason behind a double varies from word to word. Often it is an added ending, sometimes the word's history, so the double is learned along with the word.
What it means
noun. A period of one thousand years.
Other words with this trap
Try it on real words
Five words, read aloud and typed from memory with autocorrect off. About a minute, no signup.
Play today's Daily FiveSpellingIQ is a skill rating for spelling ability, not a clinical or psychometric IQ measure. American English is canonical; common variants are accepted.