Ample describes an abundance of something. An ample supply of apple muffins at the bake sale is a good thing, as is ample legroom in your new van — but if the vet notices your dog's ample waistline, you might have to put Fido on a diet.
Like amplify (crank up the volume), ample is from the Latin word amplus, meaning "large or spacious." Ample can be enough or even too much of something. It's great when there's ample parking or ample snacks for a hike, and we'd all be happy if we had ample time and money. But there are things that some people don't want more of — if your principal has ample evidence that you started the food fight in the cafeteria, you're probably going to end up in detention.