What are the rules for using comparative and superlative forms of adjectives and adverbs?

The rules for using comparative and superlative forms of adjectives and adverbs are as follows:

1. Comparative Form of Adjectives:
- For most adjectives, the comparative form is created by adding "-er" to the end of the adjective. For example: "taller," "faster," "smarter."
- If the adjective ends in "e," only "-r" is added. For example: "nicer," "braver."
- If the adjective ends in a consonant followed by a single vowel, and the last syllable is stressed, the final consonant is doubled before adding "-er." For example: "bigger," "thinner."
- Some adjectives have irregular comparative forms. For example: "good" becomes "better," "bad" becomes "worse," "far" becomes "farther" or "further."

2. Superlative Form of Adjectives:
- For most adjectives, the superlative form is created by adding "-est" to the end of the adjective. For example: "tallest," "fastest," "smartest."
- If the adjective ends in "e," only "-st" is added. For example: "nicest," "bravest."
- If the adjective ends in a consonant followed by a single vowel, and the last syllable is stressed, the final consonant is doubled before adding "-est." For example: "biggest," "thinnest."
- Some adjectives have irregular superlative forms. For example: "good" becomes "best," "bad" becomes "worst," "far" becomes "farthest" or "furthest."

3. Comparative and Superlative Form of Adverbs:
- Most adverbs form their comparative and superlative forms by adding "-er" and "-est" respectively, just like adjectives. For example: "quickly" becomes "more quickly" (comparative) and "most quickly" (superlative).
- However, some adverbs have irregular comparative and superlative forms. For example: "well" becomes "better" (comparative) and "best" (superlative), "badly" becomes "worse" (comparative) and "worst" (superlative).

4. Exceptions:
- Some adjectives and adverbs do not follow the regular rules and have completely different comparative and superlative forms. For example: "good" becomes "better" (comparative) and "best" (superlative), "bad" becomes "worse" (comparative) and "worst" (superlative).

It is important to note that when comparing two things, the comparative form is used, and when comparing more than two things, the superlative form is used. Additionally, the words "more" and "most" can be used before adjectives and adverbs to indicate the comparative and superlative forms respectively, especially for longer adjectives and adverbs.