Clients so often confuse the words fast and quick (as do many native speakers), so I will finally answer the question:
What is the difference between fast and quick?
Fast refers to speed of action or movement.
- A fast train.
- A fast runner.
Quick refers to the length of time an action or event takes.
- A quick journey.
- A quick run.
Let’s use fast and quick in the same sentence.
- They had a quick journey because the train was fast.
- It was a quick job because he is a fast worker.
Quick can refer to speed if the movement is abrupt and not sustained.
- Be quick, and grab that seat.