"useful"是英语中表示"有用"的形容词。它来自古英语"þurfan",意思是"需要"或"必要"。
例句1: This tool is very useful for cutting wood. (这个工具对于切木材很有用。)
例句2: The information provided in this book is useful for anyone studying economics. (这本书中提供的信息对于任何学习经济学的人都有用。)
例句3: She gave me some useful advice on how to study for the exam. (她给了我一些关于如何备考的有用建议。)