Someone or something that is quick moves or does things with great speed.

Quicker is sometimes used to mean 'at a greater speed', and quickest to mean 'at the greatest speed'. Quick is sometimes used to mean 'with great speed'. Some people consider this to be non-standard.

Something that is quick takes or lasts only a short time.

Quick means happening without delay or with very little delay.

Quick is sometimes used to mean 'with very little delay'.

If you are quick to do something, you do not hesitate to do it.

If someone has a quick temper, they are easily made angry.

If someone bites their nails to the quick, they bite off all the white part at the end of each nail.

If something cuts you to the quick, it makes you feel very upset.