Why is Speed Classified as a Scalar Quantity and Velocity Classified as a Vector Quantity

Answer: In Physics, we use the term scalar for measurable quantities that can be represented by size or magnitude, for example, distance, speed, etc. Vectors are those parameters that have both direction and definite magnitude. For example velocity, force, and field strength have direction in addition to magnitude. 

Speed cannot be expressed with a specified direction and thus portrays only magnitude; therefore, we call it a scalar quantity. On the other hand, velocity has a proper direction unlike speed and is thus referred to as a vector quantity.