Difficult, Hard
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 difficult? It's also difficult.
むずかしい
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: It's awfully difficult to load a cow into your Moo-zooka (むずか). Click. Boom!
それってそんなに難しいことなの？
Is that really so hard to do?
ちょっと私には難しそうだし、やめておくよ。
That sounds a little too difficult for me, so I'm not going to do it.
このゲーム、難しすぎて全然クリアできない。
This game is too difficult to clear.