Translation of "Illusion" in Chinese

- It was all an illusion?
- Was it all an illusion?

那全是幻觉吗？

Everything you saw was an illusion.

你看到的都是幻觉。

He had the illusion that he was a genius.

他幻想自己是個天才。

This looks longer than that, but it is an optical illusion.

這個看起來比那個還長，但這不過是種錯視罷了。