Sharp
Sharp (edge)
Having a thin edge or point that cuts easily.
Be careful, that knife is very sharp.
Sharp (clever)
Quick to notice and understand things.
Kabir is sharp; he spotted the mistake at once.
Sharp (exact time)
Exactly at the stated time, not a minute late.
The exam starts at nine o'clock sharp.
Remember: Sharp always means precise: a precise edge, a precise mind, a precise time.