• 留学りゅうがく — studying abroad
• 留守るす — absence from home
• 保留ほりゅう — holding off, pending
• 留意りゅうい — paying attention
• 書かき留とめ — registered mail
• 居留きょりゅう — residence (in a foreign country)
• 留年りゅうねん — repeating a school year

留 combines 田 (rice field) with 卯 (phonetic). It originally meant “to confine” or “keep in place,” and today it extends to ideas of staying, remaining, or detaining.

彼かれは 日本にほんに 留学りゅうがくしています。
He is studying abroad in Japan.

今いまは 留守るすにしています。
I’m not home right now.