There are many reasons this word needs defined, and for now, I don't think I need to explain them. Once you understand this definition, I think you will see it too.
Here is what faith is not: faith is not wanting to believe something that we actually don't. And yes, faith IS opposed to doubt. Here's why:
The actual definition of faith by the secular dictionary that a simple internet search produces is this:
Faith is complete trust or confidence in someone or something.
Dallas Willard further defines it by saying that faith is relying on something as if it were so. It means you are prepared to act without thinking as if it were so.
You actually have faith in many things throughout your everyday life.
You have faith that, when proceeding through a green light, that the cars from the other direction are going to stop at their red light. You behave as if it were so.
You have faith that your car is going to start in the morning when you turn the key in the ignition. You behave as if it were so. Etc.
Faith is not the same thing as knowledge, but the two go together. As Willard writes in Knowing Christ Today...
But it is possible, and a very good thing, to have knowledge of the same things we have faith in. Knowledge strengthens faith, sometimes by allowing us to grasp an item of faith in such a way that it also becomes an item of knowledge. Knowledge also can and often has laid a foundation for faith. We do often believe things because we have come to know them, and that is an ideal condition of belief. On the other hand, faith commonly acts as a framework and guide for the development and use of knowledge. Neither is complete without the other.
For now, the bottom line is this: when you think or speak of your faith...are you prepared to act without thinking as if it were so? Then, that's faith!
