Comparison of adjectives and adverbs

Comparatives of adjectives are formed with -er or with more.
Superlatives are formed with -est or with most.
Comparatives and superlatives of adverbs are normally formed with more and most, though there are some exceptions.

Adjectives of one syllable: add
-er and -est:
Strong stronger the strongest
Wise wiser the wisest
Dry drier the driest
Hot hotter the hottest

People grow older and wiser every day.

Some are irregular:
Bad worse the worst
Good better the best
Far further the furthest
Far farther the farthest
Little less the least
Much more the most
Many more the most

Sunny weather is better than rainy weather.
Stormy weather is definitely the worst.

Adjectives of two or more syllables take more and most except two-syllable adjectives which end in -y:
Famous more famous the most famous
Beautiful more beautiful the most beautiful
Funny funnier the funniest

Elvis Presley was one of the most famous rock musicians in the world.
Jaan is a famous musician in his village.

The following two-syllable adjectives can take either -er/-est or more/most:
Common, cruel, gentle, handsome, likely, mature, narrow, pleasant, polite, shallow, simple, stupid.
Stupid stupider the stupidest
Stupid more stupid the most stupid

Most adverbs take more and most:
Easily more easily most easily
Loudly more loudly most loudly

I wake up easily, because my alarm clock rings loudly.
My brother wakes up more easily, because his alarm clock rings more loudly.

Some are irregular:
Well better best
Badly worse worst

Adverbs with the same form as adjectives form comparatives and superlatives in the same way as adjectives:
Fast faster fastest
Early earlier earliest
Hard harder hardest

The horse is running fast.
The sheep is running faster than the horse.
The dog is running fastest.