* A push or pull that can change an object's motion. This is the most basic definition. Forces can start objects moving, stop them, or change their direction.
* An interaction between two objects. Forces are never isolated. They always involve at least two things interacting. For example, gravity is a force of attraction between two objects with mass.
* Something that can cause an object to accelerate. Acceleration means a change in speed or direction. A force is required to make something accelerate.
* A vector quantity with both magnitude and direction. Forces have both strength (magnitude) and a specific direction in which they act.
Let me know if you'd like more examples or explanation!
