speed is the distance traveled per unit time, and it is the rate at which something happens; "the project advanced with gratifying speed". While velocity is the rate of speed with which something happens; rapidity of action or reaction.
Additional answer
I don't understand any of the above. Speed is the rate that something moves, but without a particular direction. Velocity is the speed in a particular direction. Velocity is a scientific quantity, really. You probably wouldn't make this distinction in eveyday life.
If no direction is mentioned, then you have a speed. Example: "30 miles per hour". If the direction is mentioned, then you have a velocity. Example: "30 miles per hour north".
Speed is the magnitude of distance travelled per unit time, whereas velocity depends on the magnitude of distance travelled as well as the direction of motion. Speed is a scalar quantity, velocity is a vector. Speed cannot be negative, velocity can be negative. Average speed of an object after travelling a certain distance is always non-zero, but for velocity the average velocity can be zero (this follows from the previous idea).
velocity is speed with direction; velocity is a vector and speed is a scalar
Speed has no direction, velocity does.
Instantaneous speed is the magnitude of the velocity. Velocity also states the [direction] of the speed.
If no direction is mentioned, then you have a speed. Example: "30 miles per hour". If the direction is mentioned, then you have a velocity. Example: "30 miles per hour north".
Velocity is a vector: it has a direction. The others are all scalars. The dimensions of the scalars are Speed : [LT-1] Time: [T] Distance: [L]
Speed is the magnitude of distance travelled per unit time, whereas velocity depends on the magnitude of distance travelled as well as the direction of motion. Speed is a scalar quantity, velocity is a vector. Speed cannot be negative, velocity can be negative. Average speed of an object after travelling a certain distance is always non-zero, but for velocity the average velocity can be zero (this follows from the previous idea).
velocity is speed with direction; velocity is a vector and speed is a scalar
Speed in a given direction is velocity.
Speed has no direction, velocity does.
Velocity and speed are not synonyms.
SPEED has the speed only; while VELOCITY has the direction and the speed.
Instantaneous speed is the magnitude of the velocity. Velocity also states the [direction] of the speed.
Speed in a given direction is called velocity.
Well velocity is basically the same thing as speed but with direction (velocity can be negative or positive and speed is always positive). l velocity l = speed So a change in velocity means a change in speed.
Velocity is speed with a direction