• 悪夢あくむ — nightmare
• 夢中むちゅう — be hooked on 〜
• 夢想むそう — fantasy / daydream
• 夢見ゆめみ — dreaming / to see a dream
• 夢幻むげん — dreamlike / illusion

The upper part of 夢 suggests a sleeper beneath a roof, while the bottom contains 夕 (evening), evoking visions that come at night.be hooked on~Beyond literal dreams, it also conveys aspirations and the fleeting, illusion-like quality of imagination.

こどもの頃ころの夢ゆめは 宇宙飛行士うちゅうひこうしになることでした。
My childhood dream was to become an astronaut.

昨夜さくやは 変へんな 夢ゆめを見みました。
I had a strange dream last night.