IPA: /ˈbraɪtəst/
KK: /braɪtɪst/
The most full of light or color; shining strongly or vividly.
The sun is the brightest object in the sky during the day.
Comparative: brighter
Superlative: brightest
Brightest → It is formed from "bright" (from Old English "beorht", meaning shining or radiant) and "-est" (a superlative suffix indicating the highest degree). The word "brightest" means the most shining or radiant among others.
Think of something that is the "most shining" — "bright" means shining, and "-est" shows it is the highest degree of brightness.