COMPARISONS

What is a comparison?
Comparison is a rhetorical or literary device in which a writer compares or contrast two people, places, places, things, or ideas. In our everyday life, we compare people and things to express ourselves vividly. So when we say, "as lazy as a snail" you compare two different entities to show similarity i.e. someone's laziness to the slow pace of a snail.
When we want to compare two or more nouns using adjectives, we use the comparative and superlative forms of the adjective to show the comparison between the nouns.

Example:
Honey is sweet, sugar is sweeter but victory is the sweetest.

In this sentence, we are comparing the three nouns using the positive, comparative and superlative forms of the word "sweet".

There are three form of comparison:

1. Positive Form
There are the simple adjectives that simply describe the nouns without comparing it to another. (big, sweet, clean, etc.)
          She has a big black dog.
          He is a sweet boy.
          The motorcycle is clean.

2. Comparative Form
These are used when we are comparing two nouns and need to show which noun possesses the adjective or character in a greater or lesser amount, when compared with the other. (bigger, sweeter, cleaner, etc.)
          I have a big dog but hers is bigger.
          He is sweeter than the other boys.
          The motorcycle is cleaner than before.

3. Superlative Form
This form is used when three or more nouns are being compared and we need to show that one or more of the nouns posses the adjective or characteristic to the highest amount possible. We usually add 'the' before the superlative form. (biggest, sweetest, cleanest, etc.)
          She has the biggest dog in the colony.
          He is the sweetest boy in his class.
          The motorcycle is the cleanest thing in the house.

Making Comparatives and Superlatives
There are certain rules that must be followed in the making of the comparatives and superlatives of the adjectives. Not all adjectives form their comparatives and superlatives in the same way and there are also some irregular adjectives that form completely different comparative and superlative forms.

Single Syllable Words and Double Syllable Words ending with -y, -er, -ow, -le -
We use ‘-er’ to make the comparative and ‘-est’ to make the superlative.

Positive	Comparative	Superlative
Black	Blacker	Blackest
Fair	Fairer	Fairest
Clever	Cleverer	Cleverest

When there is a silent ‘e’ at the end of the positive form, we remove that and add ‘-er’ and ‘-est’

Positive	Comparative	Superlative
Nice	Nicer	Nicest
Late	Later	Latest

When the adjective ends with a ‘y’, we convert the ‘y’ into ‘i’ before adding ‘-er’ and ‘-est’

Positive	Comparative	Superlative
Pretty	Prettier	Prettiest
Lazy	Lazier	Laziest

If the adjective is a small one with little stress on the vowel, we double the last consonant.

Positive	Comparative	Superlative
Hot	Hotter	Hottest
Wet	Wetter	Wettest

Other Words with Two or More Syllables -

For other double syllable words that do not end with -y, -er, -ow, -le, and for adjectives with more than two syllables we use more and most to form the comparatives and superlatives.

Positive	Comparative	Superlative
Difficult	More Difficult	Most Difficult
Careful	More Careful	Most Careful
Handsome	More Handsome	Most Handsome
Interesting	More Interesting	Most Interesting

Special Adjectives -

There a few adjectives that can use both ‘-er and -est’ and ‘more’ and ‘most’ to form their comparative and superlative forms. The distinction between these is that ‘-er and -est’ are used when we are comparing the noun to another noun and ‘more’ and ‘most’ is used when we are comparing characteristics within the noun.

Positive	Comparative	Superlative	Example
Clever	Cleverer/ More Clever	Cleverest/ Most Clever	He is cleverer than her. He is more clever than studious.
Quiet	Quieter/ More Quiet	Quietest/ Most Quiet	This is the most quiet it gets here. This is the quietest place.
Brave	Braver/ More Brave	Bravest/ Most Brave	She is braver than other girls. She was more brave than afraid.
Sure	Surer/ More Sure	Surest/ Most Sure	He was surer of the result than others. You’ll be more sure about the concept after you read the chapter.

Irregular Comparisons -

These adjectives do not make their comparative and superlative forms using the rules above. Their comparative and superlative forms are different words altogether.

Positive	Comparative	Superlative
Bad	Worse	Worst
Good	Better	Best
Far (place & time)	Futher	Furthest
Far (place)	Father	Farthest
Old (people)	Elder	Eldest
Little (amount)	Less	Least
Late (order)	Latter	Last

Sources:
http://literarydevices.net/comparison/
http://www.englisch-hilfen.de/en/grammar/adjektive_steig.htm
http://www.englishleap.com/grammar/comparative-superlative
http://www.tipsbelajarbahasainggris.com/perbandingan-kata-sifat/