That's a good question! It is a very subtle difference. While the definitions may be similar, they each have their own nuances. "Influence" is used to imply power- such as that of a public figure or celebrity. "Affect" is more gentle in the way it changes something. And "impact" is more forceful or strongly noticed. Here are some examples: The candidates used propaganda to influence the voters opinions. You could see the news about the accident really affected him. I think the unexpected collapse of the building impacted the commissions new policies on building permits. These words could easily be interchanged but they each imply a different way of bringing about the change. Hope that helps!

The basic difference between influence and impact is that influence is the power to affect, control or manipulate something or someone; the ability to change the development of fluctuating things such as conduct, thoughts or decisions while impact is the force or energy of a collision of two objects while effect is the results (end process)of the state.