IPA: /ˈhaɪ.ɪst/
KK: /ˈhaɪɪst/
The greatest in height or level; the most elevated.
Mount Everest is the highest mountain in the world.
Comparative: higher
Superlative: highest
Highest → It is formed from "high" (from Old English "hēah", meaning elevated or tall) and the suffix "-est" (meaning the most). The word "highest" means the most elevated or tall compared to others.
Think of something that is the "most elevated" — "high" means tall, and "-est" indicates the highest degree.
No commonly confused words.