Adjectives with many syllables cannot just add -er and -est for comparative and superlative forms. These multi-syllable adjectives need to use the words more or less to show comparative and the words most or least to show superlative.
Here are some examples where more, most, less, and least modify an adjective:
John’s idea is more illogical than Cheryl’s idea.
Jim’s idea is the most illogical of all.
I studied for the less important test first..
Tomorrow I will take the least important test of all.
The Ferris wheel is more exciting that the train.
The roller coaster is the most exciting ride at the park.
The picture I painted is less colorful than the picture on your wall.
The painting by Dali is the least colorful picture of all.
Use more and less when comparing two multi-syllable adjectives. Use most and least when comparing three or more multi-syllable adjectives.
▶It’s your turn: Fill the correct adjective into the blank. Janet’s flip in the gymnastics contest was more stunning than mine, but Barbara’s cartwheel was the ______ stunning performance of all.