A vector quantity. Because velocity involves a direction as well as speed, a body can accelerate if it changes direction even if it does not change speed. Think about this.
Force is a specific, well-defined idea.
It isn't another word for tendency, speed, or mass. Just the absence of external forces. For example, it's harder to push an ocean liner than a toy boat. That's because as m goes up, for a given force, a goes down. This is sometimes called the centripetal .