In English grammar, a superlative is a form of adjective or adverb that indicates the highest order or the extreme degree of a quality surpassing all others. For example, when you describe three thin people, John, George and Bob, you would probably say “John is thin” where “thin" is basically an adjective. “George is thinner than John" where “thinner" is a comparative form. “Bob is the thinnest in class” is a superlative form where Bob is compared to the rest. Thus a superlative is used to compare three or more things and is usually preceded by the word “the”.
The superlative as a noun is an exaggerated form of expression used generally to praise someone or something. As an adjective, the superlative form is used to indicate the highest degree of a quality. In English the superlative is formed by either adding the suffix -est or the word “most or “least” before the positive form of the adjective or adverb. The superlative is always preceded by the definite article ‘the’ and is followed by a preposition and nouns of which it is the best. For instance "Bill Gates is the richest man in the world."
Superlatives make the language more colorful but one has to exercise caution in the use of superlatives to avoid any repetition and exaggeration. Superlative adjectives are used to describe or compare three or more items. In other words they are used to describe the highest degree of quality present in a person or thing in comparison with other things of the same class. For example “Mariah is the most beautiful woman in the party tonight.”
Certain adjectives take the irregular forms in comparative as well as superlative degree as in the words "good, bad, little, far , much/some/many" which take the superlatives, "best, worst, least, most, furthest" respectively. Generally superlatives are not used with words such as complete, full, or empty as these words already denote a totality or absence. But however the use of the superlative with these words occurs in modern speech and writing, more to convey a figurative sense of the meaning. Sometimes the word “least "is used to indicate a comparison as in “careful, less careful, least careful”, “powerful less powerful, least powerful”, “dangerous, less dangerous, least dangerous," " famous, more famous ,most famous" etc.