For short adjectives (one syllable), add "-er" or "-est" (e.g., "big" → "bigger," "biggest").
For longer adjectives (two or more syllables), use "more" or "most" (e.g., "beautiful" → "more beautiful," "most beautiful").
For adjectives ending in "y," change "y" to "i" and add "-er" or "-est" (e.g., "happy" → "happier," "happiest").