celer- (Latin: fast, speed, swift, rapid).Compare this with brady- for words with opposite meanings.accelerant: 
A substance that is used to intensify a fire.
 
accelerate, accelerated: 
1. To move increasigly quickly, or cause something to move faster.  
2. To happen or develop faster, or cause something to happen or develop faster. acceleration: 
1. The rate at which something increases in velocity.  
2. An increase in the rate at which something happens or develops. accelerator: 
1. A pedal or other control mechanism used to cause a vehicle to increase speed.  
2. LA machine used to increase the velocity, and hence the kinetic energy, of subatomic particles or nuclei, usually in preparation for collision with a target. accelerograph: 
An instrument for recording the acceleration of earth-tremors.
 
accelerometer: 
1. An instrument or device for measuring acceleration or speed.  
2. An instrument for ascertaining the acceleration of a moving body or for measuring mechanical vibrations. celeripedean: 
A fast runner; swift footed.
 
celerity: 
Swiftness, speed. Now chiefly (as distinguished from velocity) with reference to the movements or actions of living beings.
 
decelerate, deceleration: 
To diminish the speed of; to cause to go slower. 
 
decelerator: 
An apparatus for reducing the speed of an engine.
 
decelerometer: 
An instrument for ascertaining the deceleration of a moving body.
 
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