- speed
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Analogous words: *celerity, legerity, alacrity: fleetness, rapidity, swiftness, quickness (see corresponding adjectives at FAST): velocity, pace, headway (see SPEED)2 Speed, velocity, momentum, impetus, pace, headway are comparable but not all mutually synonymous terms that basically apply to motion through space.Speed (see also HASTE n) denotes rate of motion, a value computable by dividing the distance covered by the time taken{
a car that covers 300 miles in 6 hours has an average speed of 50 miles an hour
}Velocity denotes the speed of something that is directed along a given path. Ordinarily velocity suggests rate of motion in a straight line (linear velocity) or in an arc or circle (angular velocity){the velocity of a bullet
}{the velocity of a skier
}{velocity of a wind
}{velocity of light
}{a body rotating about a fixed axis with a constant angular velocity
}Momentum in general or casual use may take the place of speed or velocity, but in technical use it denotes not rate of motion but quantity of motion, a value determinable by multiplying the mass of a moving body by its velocity{a falling stone gathers momentum
}{the momentum of an iron ball rolling down an inclined plane is greater than that of a cork ball of the same diameter rolling with the same velocity
}{as photons are always in motion, we may also speak of the momentum of a photon, much as we speak of the momentum of a motorcar— Jeans
}Impetus (see also STIMULUS) is a popular rather than technical synonym of momentum. In practice it is a closer synonym of impulse in the sense of the effect of an impelling force, for it regularly carries an implication of a rushing upon or an onset, with the result that it usually suggests great momentum or implies a powerful driving force as the cause of such momentum{whether the steam . . . retains sufficient impetus to carry it to our shores— T. H. Huxley
}{the circulating blood receives a new impetus from the contraction of the ventricles of the heart
}Pace belongs here not as a technical term but as a term in general use to denote the speed of or as if of one (as a person or horse) going afoot{he set the pace for his companions on the hike
}{the pace was too slow for the rest of the party
}Pace often finds extended use in describing such things as activities, progress, or rate of production{keep pace with the times
}{the factories were asked to increase their pace
}{in New York he had moved on from speed to speed and from height to height, keeping pace with all the most magnificent developments in the furious city— Wolfe
}Headway basically applies to motion forward and in this sense is used chiefly in reference to ships{he started the screw turning until the African Queen was just making headway against the current— Forester
}However it frequently denotes rate of movement ahead and then is used in reference not only to ships but to whatever is capable of advancing or making progress{our mutual security program had suffered a year of lost headway— Barnett
}{the independent movements of nominalism and German mysticism made great headway—Thilly[i]
}speed vb Speed, accelerate, quicken, hasten, hurry, precipitate can mean to go or make go fast or faster.Speed emphasizes rapidity of motion or progress; as a transitive verb it suggests an increase in tempo; as an intransitive verb, a high degree of swiftness{speed up an engine
}{speed up the work in a factory
}{the bullet sped through the air
}{arrested for speeding
}{the stoutest of the boatmen seized the staff out of turn and sped our craft forward— Wain
}Accelerate stresses increase in rate of motion or progress; it does not necessarily imply speed{accelerated his pace so as to overtake the leaders
}{a rich soil accelerates the growth of most plants
}{accelerate the speed of a car
}{History of late has accelerated her pace. Where once she moved slowly . . . she has within the past decade raced forward jet-propelled— J. M. Brown
}{excitement was accelerating moment by moment, like the wheels of the train— Capote
}Quicken stresses shortening of the time consumed, often with a suggestion of animation or stimulation{exercise quickens the pulse
}{a broad and continuous education that quickens understanding of the modern world— Sidney Hook
}Hasten implies urgent quickness or a quick or premature outcome{has-tened to apologize
}{the annoyance and terror he lived in must have greatly hastened his early and unhappy death— Stevenson
}{the science of archaeology is advancing into the past almost as rapidly as physics and electronics are hastening the future— Time
}Hurry implies haste that causes confusion or prevents concentrated attention{his aim was hurried and his shot went wide of the mark
}{a second fear . . . which madly hurries her she knows not whither— Shak
}{these defects might pass more easily in a turbulent romanticist, hurrying pell-mell to get expressed some moving and dramatic scene, careless of details— Fry
}Precipitate implies impetuousness, suddenness, or abruptness{men will not bide their time, but will insist on precipitating the march of affairs— Buckle
}{its ruin was precipitated by religious persecution— J. R. Green
}
New Dictionary of Synonyms. 2014.
