When comparing two things one uses the comparative (previous lesson); however, for comparisons in larger groups, you must use the superlative. The superlative designates extremes: the best, the first, the worst, the last, etc.

A. It is the word "most" or the ending "--est" that designates the superlative. 

B. The compared term (adjective or adverb) will be preceded by the definite article:

C. Unlike the comparative, the superlative is not followed by "than": instead, one uses "of," followed by the context of the comparison (although this context is sometimes implicit):

Irregular forms

Monosyllabic adjectives (and several common two-syllable adjectives) take the ending "--est" in superlatives of superiority, and thus will not use the adverb "most." However, these same adjectives will use "less," like other adjectives, in superlatives of inferiority:
young --> the youngest,         tall --> the tallest,        old --> the oldest

>If the adjective ends in "--y" the "y" becomes "i":
heavy --> the heaviest,        early --> the earliest,        busy --> the busiest,        healthy --> the healthiest,        chilly --> the chilliest

>If the adjective ends in "--e" one adds only "--st" :
wise --> the wisest,        large --> the largest,        simple --> the simplest,        late --> the latest,

>If the adjective ends in "single vowel + consonant," the consonant is doubled and one adds "--est":
red --> the reddest,        big --> the biggest,        thin --> the thinnest,        hot --> the hottest

>Some very common superlatives have irregular forms:
good --> the best,        bad --> the worst,        far --> the farthest,

>Some adjectives exist only in superlative form:
the first,        the last