Great
Excellent, Admirable, Remarkable
い adjective
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of greatness? Great!
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
The only thing a great person doesn't do is make errors (えら). That's what makes them so great. They can always sense when an error is about to happen and they correct it before it even has a chance!
社長がそんなに偉いんですか？
What makes the company president so great?