However, this action necessitates that object 2 also act to change the motion of object 1. The words can be replaced by mathematical equations that condense the length of the statement of these laws, but still, the deep ideas are in there. Forces are operationally defined. You know a force is acting if something which has a mass is changing its motion. If a force is acting, it is due to an external object acting on the thing whose motion is changing.
Many forces are contact forces , i.e. they act only while two objects are physically touching.
Examples are gravitional, electrical, and magnetic forces. Newton's Laws of Motion apply to both kinds of forces. The bold face type indicates that force has the characteristics of a vector, namely it must be specified by direction and magnitude. Force is not exactly a vector since you must also specify what the force acts on before it is truly defined. There are various types of forces to deal with in freshman physics.