Comparatives and Superlatives

FORMS

Regular one-syllable adjectives:
- add -er and -est to the adjective: cheap(Adjective)-cheaper(Comparative)-the cheapest(Superlative)
- add -r and -st to adjectives ending in -e: late(Adjective)-later(Comparative)-the latest(Superlative)
- double the consonant of adjectives ending in a short vowel and a consonant, and add -er and -est: thin(Adjective)-thinner(Comparative)-the thinnest(Superlative)

Regular adjectives with more than one syllable:
- use more and most in front of the adjective: sincere(Adjective)-more sincere(Comparative)-the most sincere(Superlative)
- change -y to -i and add -er and -est to adjectives ending in -y after a consonant: happy(Adjective)-happier(Comparative)-the happiest(Superlative)
- a limited number of two-syllable adjectives can form the comparative and superlative in two ways:  stupid(Adjective)-stupider/more stupid(Comparative)-the stupidest/the most stupidest(Superlative) 
- most adverbs form their comparative and superlative with more and most: quietly(Adverb)-more quietly(Comparative)-the most quietly(Superlative)

Irregular forms:
- adjectives: good/better/the best - bad/worse/the worst - far/further/the further - old/older/the oldest
- adverbs: well/better/the best - badly/worse/the worst - little/less/the least - much/more/the most
- determiners: little/less/the least - few/fewer/the fewest - much/more/the most


USE

To talk about people or things that are different in some way we use:
- Comparative forms of adjectives/adverbs + than: I think listening is more difficult than reading.
- Superlative forms of adjectives/adverbs: That's the nicest thing you've said to me all day.
- Less...than and the least: That's my least favourite track on the album.

As .. as
For people or things that are the same in some way we use as + adjective/adverb + as: She's as intelligent as her brother.
So can replace the first as in negative sentences: It's not so difficult as I thought it would be.
The same + noun + as: My mum's the same age as my dad.

The + comparative, the + comparative:
We use this structure for things which occur together: The more money I have, the faster I spend it.