Formation of comparative and superlative of adjectives
Adjectives of one or two syllables form the comparative by adding "er" and the superlative by adding "est". e.g. : fast, faster, fastest.
Adjectives of more than two syllables form the comparative with "more" and the superlative with "most". e.g. : beautiful, more beautiful, most beautiful.
Some adjectives such as clever, stupid, narrow, gentle, freindly, etc form the comparative and superlative either by er/est or withmore/most.
e.g. : clever- cleverer-clevest OR clever-more clever-most clever
One-syllable adjectives ending in "e" take "r" in the comparative and "st" in the superlative form. e.g. : large-larger-largest
Two-syllable adjectives ending in "y" turn the "y" into "i" and then take er/est. e.g. : happy-happier-happiest
Adjectives ending in a streesed vowel between two consonants double the final consonant and then take er/est.
e.g. : big-bigger-biggest BUT old-older-oldest