negligible
So small or unimportant that it can be ignored.
Negligible means so small or unimportant that it's not worth worrying about. When something is negligible, it barely matters at all.
If you're saving up for a new bike that costs $200 and you find a nickel on the sidewalk, that five cents makes a negligible difference to your savings goal. It's technically more money, but it barely moves you closer to what you need. When scientists run experiments, they often ignore negligible amounts of error because those tiny variations won't change their conclusions. A few extra grains of salt in a recipe designed to feed fifty people? Negligible.
The word comes from the idea that something can be neglected or safely ignored. A negligible breeze won't affect a soccer game, though a strong wind certainly would. A negligible scratch on your bike frame doesn't require immediate repair, while a bent wheel definitely does.
People sometimes confuse negligible with simply “small,” but negligible specifically means small enough that it doesn't actually matter for practical purposes. The difference between 9.7 and 9.8 on a ten-point scale might be small, but it isn't negligible if you need a 9.8 to win first place.