sharp

keen, acute, sharp, shrewd

这些形容词均有“锐利的、敏锐的、机敏的”之意。
keen: 多指对复杂艰深的事物或问题有敏锐的观察和敏捷的理解。
acute: 侧重感觉敏锐，能分辨出一般人难以觉察的细微区别。
sharp: 指人头脑精明、敏锐或机警。
shrewd: 指有头脑，善于判断分析，精明过人。

名词 sharp:

1. a musical notation indicating one half step higher than the note named
2. a long thin sewing needle with a sharp point

形容词 sharp:

1. (of something seen or heard) clearly defined
   同义词：crisp
2. ending in a sharp point
   同义词：acuate, acute, needlelike
3. having or demonstrating ability to recognize or draw fine distinctions
   同义词：acute, discriminating, incisive, keen, knifelike, penetrating, penetrative, piercing
4. marked by practical hardheaded intelligence
   同义词：astute, shrewd
5. harsh
   同义词：sharp-worded, tart
6. having or emitting a high-pitched and sharp tone or tones
   同义词：piercing, shrill
7. extremely steep
   同义词：abrupt, precipitous
8. keenly and painfully felt; as if caused by a sharp edge or point
9. having or made by a thin edge or sharp point; suitable for cutting or piercing
10. raised in pitch by one chromatic semitone
11. very sudden and in great amount or degree
12. quick and forceful

副词 sharp:

1. changing suddenly in direction and degree
   同义词：sharply, acutely

1. Cats have sharp claws.
   猫有锋利的爪子。
2. Bring the object into focus if you want a sharp photograph.
   要照出清晰的照片，就要把焦点对准物体。
3. That woman has a very sharp tongue.
   那个女人说话非常尖刻。
4. I cut my finger on a sharp stone.
   我的手指被一块锋利的石头划破了。
5. It was very sharp of you to have noticed that.
   你注意到了这一点是够机灵的。