noun, の adjective
The kanji and the word are exactly the same. That means they share meanings as well.
When this kanji is a word on its own, it's actually very often written in hiragana. Still, the kanji version of the word is worth knowing, too!
Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word:
There's something inside and you wanna get to what's within. Look inside. Ooh, cheese (うち)! Your favorite. Ooh cheese, how I love you.
inner track, inner lane
This jacket has a lot of inside pockets.
The inside of this mask is pink.
I turned what was in my heart into a message.