1. 名詞
   不可數名詞: 有用, 有益
   有效, 有效性
   

   同義字詞
   account,avail,mileage,service,serviceability,serviceableness,use,utility
   

例句

1. A slow lens limits its usefulness indoors .
2. The usefulness of this product is extensive .
3. The usefulness of these SubMax tests is questionable.
4. This is the very foundation of usefulness and success in life.
5. Placed in His hands, you gain immensely in value and usefulness .
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