Comparatives and superlatives can act as modifiers as they are either adjectives or adverbs. The comparative form is restricted to comparing two things while the superlative form compares more than two things.
- Abu's older camel died last week.
(This sentence says that Abu has two camels, one of which died last week. Older modifies the camel that died.)
- Abu has the oldest camel in the desert.
(Here the superlative oldest is used, as there are more than two camels in the desert. Oldest modifies camel in the sentence.)
The word very can be an adjective or an adverb. We use it here as an adverb to modify an adjective or an adverb, but we cannot use it to modify comparatives and superlatives.
- Correct: Abu's camel is very old.
(Very modifies adjective old.)
- Correct: Abu rides his camel very slowly.
(Very modifies adverb slowly.)
- Incorrect: Abu's camel is very older than his uncle's camel.
(Very cannot modify comparative adjective older.)
- Incorrect: Abu rides his camel very more slowly.
(Very cannot modify a comparative adverb [more].)