fast ---- opposite - slow, slowly

fast   ----   opposite  -    slow, slowly

adjective

 faster, fastest

quick

1 moving or able to move quickly 

a fast car/horse 
the world's fastest runner 

2 happening in a short time or without delay

 the fastest rate of increase for years 
a fast response time 

3 able to do something quickly 

a fast learner

 FAST   ( adverb ) 1 : with great speed
▪  ▪ You're driving too fast! ▪ He ran as fast as he could. 

  ▪ This is fast becoming a national problem. ▪ You need to act fast to take advantage of this offer. 

 ▪ species that are fast disappearing = species that are disappearing fast  

▪ I don't know what caused the accident. It all happened so fast. — opposite slow, slowly

These adjectives are frequently used with the following nouns:

fast ~	quick ~	rapid ~
car	glance	change
train	look	growth
runner	reply	increase
pace	decision	decline
lane	way	progress

Fast is used especially to describe a person or thing that moves or is able to move at great speed. 

Quick is more often used to describe something that is done in a short time or without delay.

 Rapid, swift, and speedy are more formal words.

 Rapid is most commonly used to describe the speed at which something changes. It is not used to describe the speed at which something moves or is done:
 a rapid train We had a rapid coffee. 

Swift usually describes something that happens or is done quickly and immediately: a swift decision The government took swift action. 

Speedy has a similar meaning: a speedy recovery. It is used less often to talk about the speed at which something moves:a speedy carFor the use of fast and quick as adverbs, see the usage note at quick.


more info: http://oaadonline.oxfordlearnersdictionaries.com/dictionary/fast