What is an example of a comparative adjectives?

Adjectives that end in -er are comparative adjectives eg bigger smaller nicer smarter etc

Jon is taller than his brother.

For adjectives that are longer than two syllables use more before the adjective do not add -er to the adjective.

My book is more interesting than yours.

Note the adjective is followed by than.

Other examples:

more exciting more abundant more contagious more beautiful more delightful