Trying to define the meaning of interactivity could be tricky, as Chris Crawford states in his book, the art of interaction design. If we broaden the way we think about the act of defining we might find that it is in itself an interactive mechanism that has different meanings in different cultures throughout time and place, thus meaning language is in itself interactive(?)
My stand on the definition of the word interaction is that it is something that’s also happening without the participation of the language that measures it, it could easily be described as the constant occurrence of cause and effect.
If we think of it, interactivity is happening everywhere all the time. In physics, interaction is attributed as interoperability between two bodies or the force that two bodies exert on each other. Under Newton’s Third Law, these forces are always of equal size and contrast in their direction. Thus forces in nature always appear in pairs.
We might look at interaction as a constant in the world, with technology being it’s multiplier that accelerates and mediates between the different bodies. In many aspects, we might guess a ‘good interaction’ will be a harmonic one, an act that helps two bodies encounter each other with ease other than collide in an explosion.
But that is just a loose definition of the word ‘good’.