名詞 deepness:

1. the intellectual ability to penetrate deeply into ideas
   同義詞：astuteness, profundity, profoundness, depth
2. the quality of being physically deep
   同義詞：profundity, profoundness
3. a low pitch that is loud and voluminous

1. Her son's voice have acquired the deepness of a man.
   她兒子的聲音已經有了成年男人的低沈。