Comparative adjectives are used to compare two nouns, highlighting differences in their qualities. They often end in "-er" or are preceded by the word "more." For example, in the sentence "This book is more interesting than that one," the adjective "interesting" is used to compare the two books. When using comparative adjectives, it's important to follow specific rules. For one-syllable adjectives, you typically add "-er," as in "taller" or "smaller." For adjectives with two or more syllables, use "more," as in "more beautiful" or "more difficult." This helps clarify the comparison being made.