Come here, quick!
A "quick car" can do zero to 60 in 3.5 seconds.
A "fast car" can do 190 miles per hour.
In addition, we say "he drives fast", not "fastly". Oddly enough, we usually say "come, quick", not "come quickly"
We use "rapid" in reference to a fast and sudden move, done or occurring in a brief period of time.
The 1990s were a period of rapid change/growth.
His response to the accusation was rapid.
Rapid as a noun is the part of a river where the current moves with great
swiftness, but without actual waterfall or cascade;
To be continued...
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