い adjective
ふるい
そのふくは古いので、もういりません。
Those clothes are old, so I don’t need them anymore.
古いものにしがみついていては、あたらしいものをうけとることができません。
If you hold onto old stuff, you can't get anything new.
ガレージで、古いパンツをみつけた。
I found an old pair of underwear in our garage.
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 old? It's also old.
Since this word is made up of a single kanji with some hiragana attached, it's going to use the kun'yomi reading. You learned the on'yomi when learning the kanji portion, so let's use a mnemonic to help you with the reading of this word:
If you're old, you're also full (ふる) of memories. And you're probably full of old secrets. And you're full from old people food.