Comparative adjectives are used to compare differences between two nouns and follow specific rules for changing their endings based on the number of syllables. For one syllable adjectives, -er is added. For one syllable words with CVC pattern, the last consonant is doubled before adding -er. Two syllable adjectives ending in -y change to -ier, while other two syllable adjectives do not change but use more/less before them. The grammar structure for comparisons uses a subject, verb to be, comparative adjective, than, and object.