best
Better than all the others in quality or ability.
Best means better than all others in quality, ability, or excellence. When you score the best grade in your class, no one else scored higher. When a chef creates the best pasta dish at a restaurant, diners agree it surpasses every other option on the menu.
The word describes the top position in any comparison. Your best friend is the one you feel closest to and trust most. An athlete's best time is their fastest race ever. A scientist's best theory is the one that most accurately explains the evidence.
Best can also mean most suitable or most advantageous for a situation. The best route to school might be the safest or quickest, not necessarily the shortest. What's best often depends on what you're trying to accomplish: the best book for learning about ancient Rome differs from the best book for a relaxing afternoon.
Notice that best is a superlative, the highest degree of comparison: good, better, best. You might have a good idea, your friend might have a better one, but together you might develop the best solution of all.
People sometimes confuse best with favorite. Your favorite movie is the one you enjoy most personally, while the best movie might be the one most skillfully made, even if you prefer watching something else.