When comparing two things one uses the comparative; however, for comparisons in larger groups, it is the superlative which must be used. The superlative designates extremes: the best, the first, the worst, the last, etc.
The superlative operates like the comparative, with these exceptions:
A. While the word "more" or the ending "--er" signals the comparative, it is the word "most" or the ending "--est" that designates the superlative. (See irregular forms, below):
B. The compared term (adjective or adverb) will be preceded by the definite article:
B. 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):
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 --> youngest
- tall --> tallest
- old --> oldest
If the adjective ends in "--y" the "y" becomes "i":
- heavy --> heaviest
- early --> earliest
- busy --> busiest
- healthy --> healthiest
- chilly --> chilliest
If the adjective ends in "--e" one adds only "--st" :
- wise --> wisest
- large --> largest
- simple --> simplest
- late --> latest
If the adjective ends in "single vowel + consonant," the consonant is doubled and one adds "--est":
- red --> reddest
- big --> biggest
- thin --> thinnest
- hot --> hottest
Some very common superlatives have irregular forms:
- good --> best
- bad --> worst
- far --> farthest
Some adjectives exist only in superlative form:
- first
- last
Adverbs not ending in "--ly" do not use the adverb "--most" in the formation of superlatives of superiority, but use instead the ending "--est." However, these same adverbs will use "less," like other adverbs, in superlatives of inferiority:
- fast --> fastest
- hard --> hardest
And some adverbs have irregular forms:
- well --> best
- badly --> worst
- far --> farthest