'cooler' vs 'more cool' etc.

English as a Second Language English Vocabulary, Grammar and Idioms
1

what is correct,

cooler
or
more cool

or,

cleverer
or
more clever

cause, i found ‘cooler’ and ‘cleverer’ in the dictionary,
but i’ve seen some people saying ‘more cool’ or ‘more clever’

thanks.

2

Strictly speaking, in one-syllable words and some two-syllable words it’s more correct to add the suffix -er, so cooler and cleverer would be correct. Some people may say more clever in order to avoid that -erer ending.