Degree of comparison

In English grammar the degree of comparison of an adjective or adverb describes the relational value of one thing with something in another clause of a sentence.
An adjective may simply describe a quality, (the positive); it may compare the quality with that of another of its kind (comparative degree); and it may compare the quality with many or all others (superlative degree).


Traditional English grammar uses the comparative form when comparing exactly two things, and the superlative when comparing three or more, but in informal usage this may not hold.
Positive Comparative Superlative
Good Better Best
Beautiful More Beautiful Most Beautiful
Big Bigger Biggest
Tall Taller Tallest
Sincere More Sincere Most Sincere
Small Smaller Smallest

Comparative
In grammar, the comparative is the form of an adjective or adverb which denotes the degree or grade by which a person, thing, or other entity has a property or quality greater or less in extent than that of another, and is used in this context with a subordinating conjunction, such as than, as...as, etc.

Two-clause sentences
For sentences with the two clauses other two-part comparative subordinating conjunctions may be used:
as...as ("The house was as large as two put together.")
not so / not as ...as ("The coat of paint is not as [not so] fresh as it used to be.")
the same ... as ("The market square is just the same as I remember it to be.")
less / more ... than ("It cost me more than I had hoped.")

Adverbs
The adverb is determined by the -ly suffix as usual, and in a comparative phrase changes to -lier.

However, adverbs with a greater number of syllables than two, require the use of more (or less), as in ("this sofa seats three people more comfortably than the other one").

Some irregular adverbs such as fast / often may be added without the suffix, ("My new car starts more quickly than the old one."), or ("My new car starts quicker/faster than the old one."), and ("I go into town more often than I used to.").

In grammar the superlative of an adjective or adverb is the greatest form of adjective or adverb which indicates that something has some feature to a greater degree than anything it is being compared to in a given context.

For example, if AJ is 45, Deniz is 35, and Jeff is 25, AJ is the oldest of the three, because his age transcends those of Deniz and Jeff in one direction, while Jeff is the youngest, because his age transcends those of AJ and Deniz in the other direction.

If David, who is 60, and Vincent, who is 20, join the group, David now becomes the oldest and Vincent the youngest.

In English, the superlative and the comparative are created by inflecting adjectives or adverbs.

The structure of a superlative consists normally of the positive stem of the adjective or adverb, plus the suffix -est, or (especially in words of a Latin or Romance origin) the modifier "most" or "least" before the adjective or adverb.

It always has the definite article and is completed by "of" or another preposition plus one or more nouns of entities that it surpasses to the highest or greatest degree, such as in "he is the tallest of/in the class," or "the town is the most beautiful in the country."

Examples:
This is the biggest house in this street. (Superlative)
This house is bigger than any other house in this street. (Comparative)
No other house in this street is as big as this one. (Positive)

The term “biggest” is the superlative version of the term “big”. All the three sentences mean the same meaning.

He is the most intelligent in this class. (Superlative)
He is more intelligent than other boys in the class. (Comparative)
No other boy is as intelligent as this boy. (Positive)
The term “most intelligent” is superlative version of the term “intelligent”. Both these sentences convey the same meaning.